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Java™ Programmi

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SL-275

Copyrig

This pro lation. No part of this product or document maybe repro

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Sun, Sun emarks of Sun Microsystems, Inc. in the U.S. andother co

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The OPE es the pioneering efforts of Xerox in researchingand dev ox to the Xerox Graphical User Interface, whichlicense a

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Java™ Programmi iv2006 Sun Microsystem

....................... Preface-xvi

...................................Preface-xvii

....................................Preface-xix

..................................... Preface-xx

....................................Preface-xxi

...................................Preface-xxii

..................................Preface-xxiii

..................................Preface-xxiv....................................Preface-xxv

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ng Languages, Inc. All Rights Reserved. Sun Services, Revision F.1

Course Contents

About This Course ..............................................................Course Goals ..........................................................................................Course Overview ..................................................................................Course Map ............................................................................................Topics Not Covered ..............................................................................How Prepared Are You? ......................................................................Introductions .........................................................................................How to Use the Icons ............................................................................Typographical Conventions and Symbols .......................................

Getting Started ....................................................................Objectives ...............................................................................................Relevance ................................................................................................What Is the Java™ Technology? .........................................................Primary Goals of the Java Technology ..............................................The Java Virtual Machine ....................................................................Garbage Collection ...............................................................................The Java Runtime Environment ..........................................................Operation of the JRE With a Just-In-Time (JIT) Compiler ..............JVM™ Tasks ..........................................................................................The Class Loader ...................................................................................The Bytecode Verifier ...........................................................................A Simple Java Application ...................................................................The TestGreeting Application .........................................................The Greeting Class ..............................................................................Compiling and Running the TestGreeting Program ....................

Java™ vCopyrig

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Sun Services

Programming Languageht 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1

Compile-Time Errors ............................................................................Runtime Errors ......................................................................................Java Technology Runtime Environment ...........................................

Object-Oriented Programming ...........................................Objectives ...............................................................................................Relevance ................................................................................................Software Engineering ...........................................................................The Analysis and Design Phase ..........................................................Abstraction .............................................................................................Classes as Blueprints for Objects ........................................................Declaring Java Technology Classes ....................................................Declaring Attributes .............................................................................Declaring Methods ................................................................................Accessing Object Members ..................................................................Information Hiding ...............................................................................Encapsulation ........................................................................................Declaring Constructors ........................................................................The Default Constructor ......................................................................Source File Layout ................................................................................Software Packages ................................................................................The package Statement ........................................................................The import Statement ..........................................................................Directory Layout and Packages ..........................................................Development .........................................................................................Compiling Using the -d Option .........................................................Terminology Recap ...............................................................................Using the Java Technology API Documentation ..............................Java Technology API Documentation With HTML3 .......................

Java™ viCopyrig

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.................................................. 3-5................................................... 3-6.................................................. 3-9................................................ 3-10................................................ 3-11................................................ 3-12................................................ 3-13................................................ 3-14................................................ 3-15................................................ 3-17................................................ 3-19................................................ 3-20................................................ 3-21................................................ 3-22................................................ 3-23................................................ 3-24................................................ 3-25................................................ 3-26................................................ 3-27................................................ 3-32................................................ 3-36

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Sun Services


Identifiers, Keywords, and Types ......................................Objectives ...............................................................................................Relevance ................................................................................................Comments ..............................................................................................Semicolons, Blocks, and White Space ...............................................Identifiers ...............................................................................................Java Programming Language Keywords ..........................................Primitive Types .....................................................................................Logical – boolean .................................................................................Textual – char .......................................................................................Textual – String ...................................................................................Integral – byte, short, int, and long ...............................................Floating Point – float and double ....................................................Variables, Declarations, and Assignments ........................................Java Reference Types ............................................................................Constructing and Initializing Objects ................................................Memory Allocation and Layout ..........................................................Explicit Attribute Initialization ...........................................................Executing the Constructor ...................................................................Assigning a Variable .............................................................................Assigning References ............................................................................Pass-by-Value ........................................................................................The this Reference ...............................................................................Java Programming Language Coding Conventions ........................

Expressions and Flow Control ..........................................Objectives ...............................................................................................Relevance ................................................................................................Variables and Scope ..............................................................................Variable Scope Example .......................................................................

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Sun Services


Variable Initialization ...........................................................................Initialization Before Use Principle ......................................................Operator Precedence ............................................................................Logical Operators ..................................................................................Bitwise Logical Operators ....................................................................Right-Shift Operators >> and >>> .......................................................Left-Shift Operator << ..........................................................................Shift Operator Examples ......................................................................String Concatenation With + ...............................................................Casting ....................................................................................................Promotion and Casting of Expressions .............................................Simple if, else Statements ..............................................................Complex if, else Statements ..........................................................Switch Statements .................................................................................Looping Statements ..............................................................................Special Loop Flow Control ..................................................................The break Statement ............................................................................The continue Statement .....................................................................Using break Statements with Labels .................................................Using continue Statements with Labels ..........................................

Arrays ...................................................................................Objectives ...............................................................................................Relevance ................................................................................................Declaring Arrays ...................................................................................Creating Arrays .....................................................................................Creating Reference Arrays ...................................................................Initializing Arrays .................................................................................Multidimensional Arrays .....................................................................Array Bounds ........................................................................................

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Sun Services


Using the Enhanced for Loop ............................................................Array Resizing .......................................................................................Copying Arrays .....................................................................................

Class Design ........................................................................Objectives ...............................................................................................Relevance ................................................................................................Subclassing .............................................................................................Single Inheritance ..................................................................................Access Control .......................................................................................Overriding Methods .............................................................................Overridden Methods Cannot Be Less Accessible .............................Invoking Overridden Methods ...........................................................Polymorphism .......................................................................................Virtual Method Invocation ..................................................................Heterogeneous Collections ..................................................................Polymorphic Arguments .....................................................................The instanceof Operator ...................................................................Casting Objects ......................................................................................Overloading Methods ..........................................................................Methods Using Variable Arguments .................................................Overloading Constructors ...................................................................Constructors Are Not Inherited ..........................................................Invoking Parent Class Constructors ...................................................Constructing and Initializing Objects: A Slight Reprise ..................Constructor and Initialization Examples ...........................................The Object Class ..................................................................................The equals Method ..............................................................................An equals Example .............................................................................The toString Method .........................................................................

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Sun Services


Wrapper Classes ...................................................................................Autoboxing of Primitive Types ...........................................................

Advanced Class Features ..................................................Objectives ...............................................................................................Relevance ................................................................................................The static Keyword ...........................................................................Class Attributes .....................................................................................Class Methods .......................................................................................Static Initializers ....................................................................................The final Keyword .............................................................................Final Variables .......................................................................................Blank Final Variables ............................................................................Old-Style Enumerated Type Idiom ....................................................The New Enumerated Type ................................................................Advanced Enumerated Types .............................................................Static Imports .........................................................................................Abstract Classes ....................................................................................The Solution ...........................................................................................Interfaces ................................................................................................The Flyer Example ................................................................................Multiple Interface Example .................................................................Uses of Interfaces ..................................................................................

Exceptions and Assertions ................................................Objectives ...............................................................................................Relevance ................................................................................................Exceptions and Assertions ..................................................................Exceptions ..............................................................................................Exception Example ...............................................................................

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Sun Services


The try-catch Statement ...................................................................Call Stack Mechanism ..........................................................................The finally Clause .............................................................................Exception Categories ............................................................................Common Exceptions .............................................................................The Handle or Declare Rule ................................................................Method Overriding and Exceptions ...................................................Creating Your Own Exceptions ..........................................................Handling a User-Defined Exception ..................................................Assertions ...............................................................................................Recommended Uses of Assertions .....................................................Internal Invariants .................................................................................Control Flow Invariants .......................................................................Postconditions and Class Invariants .................................................Controlling Runtime Evaluation of Assertions ................................

Text-Based Applications ....................................................Objectives ...............................................................................................Relevance ................................................................................................Command-Line Arguments ................................................................System Properties ..................................................................................The Properties Class .........................................................................Console I/O ...........................................................................................Writing to Standard Output ................................................................Reading From Standard Input ............................................................Simple Formatted Output ....................................................................Simple Formatted Input .......................................................................Files and File I/O ..................................................................................Creating a New File Object ...............................................................The File Tests and Utilities ................................................................

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Sun Services


File Stream I/O ......................................................................................File Output Example .............................................................................The Collections API ..............................................................................A Set Example ......................................................................................A List Example ....................................................................................Collections in JDK™ Version 1.1 .......................................................Generics ..................................................................................................Generic Collections API .......................................................................Compiler Warnings .............................................................................Iterators ...................................................................................................The Iterator Interface Hierarchy .........................................................Enhanced for Loop ..............................................................................

Building Java GUIs .............................................................Objectives ...............................................................................................Relevance ................................................................................................Abstract Window Toolkit ....................................................................The java.awt Package .........................................................................Containers ..............................................................................................Positioning Components ......................................................................Frames .....................................................................................................The FrameExample Class .....................................................................Example Frame ......................................................................................Panels ......................................................................................................The FrameWithPanel Class .................................................................Layout Managers ..................................................................................Default Layout Managers ....................................................................A Simple FlowLayout Example ..........................................................The FlowLayout Manager ...................................................................The FlowExample Class .......................................................................

Java™ xiiCopyrig

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Sun Services


The BorderLayout Manager ...............................................................Organization of the Border Layout Components .............................The BorderExample Class ...................................................................Example of BorderLayout ..................................................................The GridLayout Manager ...................................................................The GridExample Class .......................................................................Example of GridLayout .....................................................................The ComplexLayoutExample Class ..................................................Drawing in AWT ..................................................................................Various Shapes Drawn by the Graphics Object ..............................

GUI Event Handling .............................................................Objectives ...............................................................................................Relevance ................................................................................................What Is an Event? .................................................................................Delegation Model ..................................................................................A Listener Example ...............................................................................Event Categories ...................................................................................Method Categories and Interfaces ......................................................Complex Example .................................................................................Multiple Listeners .................................................................................Event Adapters ......................................................................................Event Handling Using Inner Classes ................................................Event Handling Using Anonymous Classes ....................................

GUI-Based Applications .....................................................Objectives ...............................................................................................Relevance ................................................................................................AWT Components ................................................................................AWT Listeners .......................................................................................

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Sun Services


How to Create a Menu .........................................................................Creating a MenuBar ...............................................................................Creating a Menu .....................................................................................Creating a MenuItem .............................................................................Creating a CheckBoxMenuItem ...........................................................Controlling Visual Aspects ..................................................................J.F.C./Swing Technology .....................................................................

Threads ................................................................................Objectives ...............................................................................................Relevance ................................................................................................Threads ...................................................................................................Creating the Thread ..............................................................................Starting the Thread ...............................................................................Thread Scheduling ................................................................................Thread Scheduling Example ...............................................................Terminating a Thread ...........................................................................Basic Control of Threads ......................................................................The join Method ..................................................................................Other Ways to Create Threads ............................................................Selecting a Way to Create Threads .....................................................Using the synchronized Keyword ...................................................The Object Lock Flag ............................................................................Releasing the Lock Flag ........................................................................Using synchronized – Putting It Together ......................................Thread State Diagram With Synchronization ...................................Deadlock .................................................................................................Thread Interaction – wait and notify ..............................................Thread Interaction .................................................................................Thread State Diagram With wait and notify ................................

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Sun Services


Monitor Model for Synchronization ..................................................The Producer Class ..............................................................................The Consumer Class ..............................................................................The SyncStack Class ............................................................................The pop Method ....................................................................................The push Method ..................................................................................The SyncTest Class ..............................................................................The SyncTest Class ..............................................................................

Advanced I/O Streams ........................................................Objectives ...............................................................................................Relevance ................................................................................................I/O Fundamentals ................................................................................Fundamental Stream Classes ..............................................................Data Within Streams .............................................................................The InputStream Methods .................................................................The OutputStream Methods ...............................................................The Reader Methods ............................................................................The Writer Methods ............................................................................Node Streams .........................................................................................A Simple Example .................................................................................Buffered Streams ...................................................................................I/O Stream Chaining ...........................................................................Processing Streams ...............................................................................The InputStream Class Hierarchy ....................................................The OutputStream Class Hierarchy ..................................................The Reader Class Hierarchy ...............................................................The Writer Class Hierarchy ...............................................................

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Sun Services


Networking ...........................................................................Objectives ...............................................................................................Relevance ................................................................................................Networking ............................................................................................Networking With Java Technology ....................................................Java Networking Model .......................................................................Minimal TCP/IP Server .......................................................................Minimal TCP/IP Client ........................................................................

Sun

Java™ Programmi

Services

ng Language

Preface

About This Course

Java™ Preface, slide xvii of xxviiCopyrig

Th d skills to:

hat leverage theuage, such asrphismrom the

ressionsructs

sing exception

Sun Services


Course Goals

is course provides you with knowledge an

• Create Java™ technology applications tobject-oriented features of the Java langencapsulation, inheritance, and polymo

• Execute a Java technology application fcommand-line

• Use Java technology data types and exp• Use Java technology flow control const• Use arrays and other data collections• Implement error-handling techniques u

handling

Java™ Preface, slide xviii of xxviiCopyrig

nterface (GUI)ents: panels,s

nality to read

rotocol/ommunicates

Sun Services


Course Goals

• Create an event-driven graphical user iby using Java technology GUI componbuttons, labels, text fields, and text area

• Implement input/output (I/O) functiofrom and write to data and text files

• Create multithreaded programs• Create a simple Transmission Control P

Internet Protocol (TCP/IP) client that cthrough sockets

Java™ Preface, slide xix of xxviiCopyrig

Th

nguage to the Java

Sun Services


Course Overview

is course describes the following areas:

• The syntax of the Java programming la• Object-oriented concepts as they apply

programming language• GUI programming• Multithreading• Networking

Sun Services

Course Map

The Java Programming Language Basics

More Object-Oriented Programming

Building Applications

Developing Graphical User Interfaces

Advanced Java Programming

Getting StartedObject-Oriented

Programming

Identifiers,Keywords, and

Types

Arrays

Class DesignAdvanced

Class Features

Text-Based

Applications

Building Java

GUIs

GUI Event

Handling

GUI-Based

Applications

Advanced

I/O StreamsThreads Networking

Expressions

and Flow Control

Exceptions

and Assertions

Java™ Programming Language Preface, slide xx of xxviiCopyright 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1

Java™ Preface, slide xxi of xxviiCopyrig

overed inlysis and Design

red in SL-110: Language

Sun Services


Topics Not Covered

• Object-oriented analysis and design – COO-226: Object-Oriented Application AnaUsing UML

• General programming concepts – CoveFundamentals of the Java™ Programming

Java™ Preface, slide xxii of xxviiCopyrig

Bef completedSL g Language, orhav

or C++t editorser, such as

Sun Services


How Prepared Are You?

ore attending this course, you should have-110: Fundamentals of the Java™ Programmin

e:

• Created and compiled programs with C• Created and edited text files using a tex• Used a World Wide Web (WWW) brow

Netscape Navigator™

Java™ Preface, slide xxiii of xxviiCopyrig

in this course

Sun Services


Introductions

• Name• Company affiliation• Title, function, and job responsibility• Experience related to topics presented • Reasons for enrolling in this course• Expectations for this course

Java™ Preface, slide xxiv of xxviiCopyrig

?

Sun Services


How to Use the Icons

Additional resources

Discussion

Note

Caution

Visual Aid

!

Java™ Preface, slide xxv of xxviiCopyrig

T ymbols

ands, files,mmingtput.and numbersramming coden.es andplaced with a

epresentby the student

Sun Services


ypographical Conventions and S

• Courier is used for the names of commdirectories, programming code, prograconstructs, and on-screen computer ou

• Courier bold is used for characters that you type, and for each line of progthat is referenced in a textual descriptio

• Courier italics is used for variablcommand-line placeholders that are rereal name or value.

• Courier italics bold is used to rvariables whose values are to be enteredas part of an activity.

Java™ Preface, slide xxvi of xxviiCopyrig

T ymbols

w words or

Sun Services


ypographical Conventions and S

• Palatino italics is used for book titles, neterms, or words that are emphasized.

Java™ Preface, slide xxvii of xxviiCopyrig

Jav e followingadd

ethods, and

es unless an.rations,e.g System

soft Windows

Sun Services


Additional Conventions

a programming language examples use thitional conventions:

• Courier is used for the class names, mkeywords.

• Methods are not followed by parenthesformal or actual parameter list is show

• Line breaks occur where there are sepaconjunctions, or white space in the cod

• If a command on the Solaris™ Operatin(Solaris OS) is different from the Microplatform, both commands are shown.

Sun

Java™ Programmi

Services

ng Language

Module 1

Getting Started

Java™ Module 1, slide 2 of 23Copyrig

ologyechnology

l Machine

a platform that

ne” and “JVM”platform.

Sun Services


Objectives

• Describe the key features of Java techn• Write, compile, and run a simple Java t

application• Describe the function of the Java Virtua

(JVM™)• Define garbage collection• List the three tasks performed by the Jav

handle code security

NOTE: The terms “Java Virtual Machimean a Virtual Machine for the Java™


mplete programs for

g language? improve on

Sun Services


Relevance

• Is the Java programming language a colanguage or is it useful only for writingthe Web?

• Why do you need another programmin• How does the Java technology platform

other language platforms?


ogy?

d applications.

Sun Services


What Is the Java™ Technol

• Java technology is:• A programming language• A development environment• An application environment• A deployment environment

• It is similar in syntax to C++.• It is used for developing both applets an


nology

uages

and clear coder:

Sun Services


Primary Goals of the Java Tech

• Provides an easy-to-use language by:• Avoiding many pitfalls of other lang• Being object-oriented• Enabling users to create streamlined

• Provides an interpreted environment fo• Improved speed of development• Code portability


ology

ead of activitye time they are

ally duringate sources

Sun Services


Primary Goals of the Java Techn

• Enables users to run more than one thr• Loads classes dynamically; that is, at th

actually needed• Supports changing programs dynamic

runtime by loading classes from dispar• Furnishes better security


ology

Th

1.

Sun Services


Primary Goals of the Java Techn

e following features fulfill these goals:

• The Java Virtual Machine (JVM™)1

• Garbage collection• The Java Runtime Environment (JRE)• JVM tool interface

The terms "Java Virtual Machine" and "JVM" mean a Virtual Machine for the Java platform


e

ons

revelopment tool

Sun Services


The Java Virtual Machin

• Provides hardware platform specificati• Reads compiled byte codes that are

platform-independent• Is implemented as software or hardwa• Is implemented in a Java technology de

or a Web browser


JVM

[CPU])

Sun Services


The Java Virtual Machine

provides definitions for the:

• Instruction set (central processing unit • Register set• Class file format• Stack• Garbage-collected heap• Memory area• Fatal error reporting• High-precision timing support


hen the code is

y Suncompliant class

environments.

Sun Services


The Java Virtual Machine

• The majority of type checking is done wcompiled.

• Implementation of the JVM approved bMicrosystems must be able to run any file.

• The JVM executes on multiple operating


ded should be

rogrammer’s

des alocation.aracteristics:ger needed

plementations

Sun Services


Garbage Collection

• Allocated memory that is no longer needeallocated.

• In other languages, deallocation is the presponsibility.

• The Java programming language provisystem-level thread to track memory al

• Garbage collection has the following ch• Checks for and frees memory no lon• Is done automatically• Can vary dramatically across JVM im


ent

Th s follows:

ser

deer

ter

e

are

e

Sun Services


The Java Runtime Environm

e Java application environment performs aCompile

TestGreeting.java

TestGreeting.class

Load from

Clasload

Bytecoverifi

Interpre

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Hardw

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javac

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hard disk,network,or othersource


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e

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Sun Services


peration of the JRE With a Just-InCompiler

Compile

TestGreeting.java

TestGreeting.class

Classloader

Bytecodeverifier

Interpreter

Runtime

Hardwar

Runtime

javac

java

g

Load fromhard disk,network,or othersource


Th

Sun Services


JVM™ Tasks

e JVM performs three main tasks:

• Loads code• Verifies code• Executes code


ution of a

in separate

Sun Services


The Class Loader

• Loads all classes necessary for the execprogram

• Maintains classes of the local file systemnamespaces

• Prevents spoofing


En

ion.rity.flows or

code are

sion of integers

Sun Services


The Bytecode Verifier

sures that:

• The code adheres to the JVM specificat• The code does not violate system integ• The code causes no operand stack over

underflows.• The parameter types for all operational

correct.• No illegal data conversions (the conver

to pointers) have occurred.


n

Th

123456789

Th

12345

Sun Services


A Simple Java Applicatio

e TestGreeting.java Application

//// Sample "Hello World" application//public class TestGreeting{public static void main (String[] args) {

Greeting hello = new Greeting(); hello.greet(); }}

e Greeting.java Class

public class Greeting {public void greet() {

System.out.println(“hi”); }}


tion

Sun Services


The TestGreetingApplica

• Comment lines• Class declaration• The main method• Method body


Sun Services


The GreetingClass

• Class declaration• The greet method


C Greeting

atically.ing command:

rrors.

Sun Services


ompiling and Running the TestProgram

• Compile TestGreeting.java:javac TestGreeting.java

• The Greeting.java is compiled autom• Run the application by using the follow

java TestGreeting

• Locate common compile and runtime e


symbolang.String)ream

estGreetingd

Sun Services


Compile-Time Errors

• javac: Command not found

• Greeting.java:4: cannot resolvesymbol : method printl (java.llocation: class java.io.PrintStSystem.out.printl("hi");

^

• TestGreet.java:4: Public class Tmust be defined in a file calle"TestGreeting.java".


in

Sun Services


Runtime Errors

• Can’t find class TestGreeting

• Exception in thread "main"java.lang.NoSuchMethodError: ma


ronment

Sun Services


Java Technology Runtime Envi

Com

pile

TestGreeting.java

TestGreeting.class

Run

time

Greeting.class

Greeting.java

JVM

UNIX® DOS JavaOS™

JVMJVM

javac

java

Also compiles

Also loads

Can run on multiple platforms

Sun

Java™ Programmi

ming

Services

ng Language

Module 2

Object-Oriented Program


ncapsulation,

ogy application

onstructor, and

public assulation

ogramming

Sun Services


Objectives

• Define modeling concepts: abstraction, eand packages

• Discuss why you can reuse Java technolcode

• Define class, member, attribute, method, cpackage

• Use the access modifiers private andappropriate for the guidelines of encap

• Invoke a method on a particular object• Use the Java technology application pr

interface (API) online documentation


e analysis and

and code reuse?ing language

language?

Sun Services


Relevance

• What is your understanding of softwardesign?

• What is your understanding of design• What features does the Java programm

possess that make it an object-oriented• Define the term object-oriented.


0s–Up)soft Windows

penLook

JDBC™

Java

Sun Services


Software Engineering

Machine Code (Late 1940s–Up)

High-Level Languages (1950s–Up) Operating Systems (196

Libraries / Functional APIs (1960s–Early 1980s)

Object-Oriented Languages (1980s–Up)

Toolkits / Frameworks / Object APIs (1990s–Up)

Fortran LISP C UNIX MicroMacOS

NASTRAN X-Windows

COBOL

TCP/IP ISAM O

SELF Smalltalk Common Lisp Object System Eiffel

AWT / J.F.C./Swing Jini™ JavaBeans™Java 2 SDK

C++

OS/360


ase

ds to do:tors and

t:ractionsstemimplify the

Sun Services


The Analysis and Design Ph

• Analysis describes what the system neeModeling the real-world, including acactivities, objects, and behaviors

• Design describes how the system does i• Modeling the relationships and inte

between objects and actors in the sy• Finding useful abstractions to help s

problem or solution


e used in many

tes and

of objects thats can be usedbehavior

Sun Services


Abstraction

• Functions – Write an algorithm once to bsituations

• Objects – Group a related set of attribubehaviors into a class

• Frameworks and APIs – Large groups support a complex activity; Frameworkas is or be modified to extend the basic


jects

s a device fromructed.n object:object includes.each object

e key features:

Sun Services


Classes as Blueprints for Ob

• In manufacturing, a blueprint describewhich many physical devices are const

• In software, a class is a description of a• A class describes the data that each • A class describes the behaviors that

exhibits.• In Java technology, classes support thre

of object-oriented programming (OOP)• Encapsulation• Inheritance• Polymorphism


lasses

Sun Services


Declaring Java Technology C

• Basic syntax of a Java class:<modifier>* class <class_name> {

<attribute_declaration>*<constructor_declaration>*<method_declaration>*

}

• Example:1 public class Vehicle {2 private double maxLoad;3 public void setMaxLoad(double value) {4 maxLoad = value;5 }6 }


e>];

Sun Services


Declaring Attributes

• Basic syntax of an attribute:<modifier>* <type> <name> [ = <initial_valu

• Examples:1 public class Foo {2 private int x;3 private float y = 10000.0F;4 private String name = "Bates Motel";5 }


t>* ) {

Sun Services


Declaring Methods

• Basic syntax of a method:<modifier>* <return_type> <name> ( <argumen

<statement>*}

• Examples:1 public class Dog {2 private int weight;3 public int getWeight() {4 return weight;5 }6 public void setWeight(int newWeight) {7 if ( newWeight > 0 ) {8 weight = newWeight;9 }10 }11 }


rs

r>

ncluding

s public

Sun Services


Accessing Object Membe

• The dot notation is: <object>.<membe• This is used to access object members, i

attributes and methods.• Examples of dot notation are:

d.setWeight(42);d.weight = 42; // only permissible if weight i


Th

+

+

+

t access to to a MyDate

ound

Sun Services


Information Hiding

e problem:

MyDate

day : int

month : int

year : int

Client code has direcinternal data (d refersobject):

d.day = 32;// invalid day

d.month = 2; d.day = 30;// plausible but wrong

d.day = d.day + 1;// no check for wrap ar


Th setters andnal data:

false

e if wrap around

+

+

+

+

+

+

-d

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Sun Services


Information Hiding

e solution:Client code must usegetters to access inter

MyDate d = new MyDate();

d.setDay(32);// invalid day, returns

d.setMonth(2);d.setDay(30);// plausible but wrong,// setDay returns false

d.setDay(d.getDay() + 1);// this will return fals// needs to occur

setDay(int) : boolean

setYear(int) : boolean

setMonth(int) : boolean

getDay() : int

getMonth() : int

getYear() : int

MyDate

ay : int

onth : int

ear : int

Verify days in month


lasscess data

Sun Services


Encapsulation

• Hides the implementation details of a c• Forces the user to use an interface to ac• Makes the code more maintainable

+setDay(int) : boolean

+setYear(int) : boolean

+setMonth(int) : boolean

+getDay() : int

+getMonth() : int

+getYear() : int

MyDate

-date : long

-isDayValid(int) : boolean


Sun Services


Declaring Constructors

• Basic syntax of a constructor:[<modifier>] <class_name> ( <argument>* ) {<statement>*

}

• Example:1 public class Dog {23 private int weight;45 public Dog() {6 weight = 42;7 }8 }


r

in every class.ructors, thecally:umentstyinstances with

onstructor.

Sun Services


The Default Constructo

• There is always at least one constructor• If the writer does not supply any const

default constructor is present automati• The default constructor takes no arg• The default constructor body is emp

• The default enables you to create objectnew Xxx()without having to write a c


ort.java file

{...}

Sun Services


Source File Layout

• Basic syntax of a Java source file is:[<package_declaration>]<import_declaration>*<class_declaration>+

• For example, the VehicleCapacityRepis:1 package shipping.reports;23 import shipping.domain.*;4 import java.util.List;5 import java.io.*;67 public class VehicleCapacityReport {8 private List vehicles;9 public void generateReport(Writer output)10 }


ystems.ackages.

icle

RiverBarge

Sun Services


Software Packages

• Packages help manage large software s• Packages can contain classes and sub-p

Veh

Truck

Company Owns 0..*

shipping

domaingui

reports


t

is:

eginning of the

ce file. is placed into

d separated by

Sun Services


The packageStatemen

• Basic syntax of the package statement package <top_pkg_name>[.<sub_pkg_name>]*;

• Examples of the statement are:package shipping.gui.reportscreens;

• Specify the package declaration at the bsource file.

• Only one package declaration per sour• If no package is declared, then the class

the default package.• Package names must be hierarchical an

dots.


:name>;

g:

ses

Sun Services


The importStatement

• Basic syntax of the import statement isimport <pkg_name>[.<sub_pkg_name>]*.<class_ORimport <pkg_name>[.<sub_pkg_name>]*.*;

• Examples of the statement are:import java.util.List;import java.io.*;import shipping.gui.reportscreens.*;

• The import statement does the followin• Precedes all class declarations• Tells the compiler where to find clas


ges

containing the

packages.

.class

Sun Services


Directory Layout and Packa

• Packages are stored in the directory treepackage name.

• An example is the shipping applicationshipping/

domain/

gui/

reports/

Vehicle.classRiverBarge.classTruck.class

VehicleCapacityReport

Company.class


J

Sun Services


DevelopmentavaProjects/

ShippingPrj/

src/

docs/

shipping/

domain/gui/reports/

classes/

shipping/

domain/gui/reports/


tion

va

Sun Services


Compiling Using the -dOp

cd JavaProjects/ShippingPrj/srcjavac -d ../classes shipping/domain/*.ja


run-time object

;iable, and data

bject;roceduresed to initialize

b-packages

Sun Services


Terminology Recap

• Class – The source-code blueprint for a• Object – An instance of a class;

also known as instance• Attribute – A data element of an object

also known as data member, instance varfield

• Method – A behavioral element of an oalso known as algorithm, function, and p

• Constructor – A method-like construct ua new object

• Package – A grouping of classes and su


API

HTML) files

s hyperlinks tot package.rarchy, avariables, a list

Sun Services


Using the Java TechnologyDocumentation

• A set of Hypertext Markup Language (provides information about the API.

• A frame describes a package and containinformation describing each class in tha

• A class document includes the class hiedescription of the class, a list of memberof constructors, and so on.

Sun Services

Java Technology APIDocumentation With HTML3

Java™ Programming Language Module 2, slide 26 of 26Copyright 2006 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision F.1

Sun

Java™ Programmi

Id Types

Services

ng Language

Module 3

entifiers, Keywords, and


identifiers

xtual typeseference variable

Sun Services


Objectives

• Use comments in a source program• Distinguish between valid and invalid • Recognize Java technology keywords• List the eight primitive types• Define literal values for numeric and te• Define the terms primitive variable and r


variableiables of class

Sun Services


Objectives

• Declare variables of class type• Construct an object using new• Describe default initialization• Describe the significance of a reference• State the consequences of assigning var

type


n variableswith object

Sun Services


Relevance

• Do you know the primitive Java types?• Can you describe the difference betwee

holding primitive values as compared references?


Th ava technologypro

// c

/* c* o*/

/** * */

Sun Services


Comments

e three permissible styles of comment in a Jgram are:

omment on one line

omment on oner more lines

documentation commentcan also span one or more lines


Space

terminated by

nd by opening

Sun Services


Semicolons, Blocks, and White

• A statement is one or more lines of codea semicolon (;):totals = a + b + c

+ d + e + f;

• A block is a collection of statements bouand closing braces:{ x = y + 1; y = x + 1;}


Space

Sun Services



• A class definition uses a special block:public class MyDate { private int day; private int month; private int year;}

• You can nest block statements.while ( i < large ) {a = a + i;// nested blockif ( a == max ) {b = b + a;a = 0;

}i = i + 1;

}


Space

in a Java

Sun Services



• Any amount of white space is permittedprogram.For example:{int x;x=23*54;}

is equivalent to:{int x;

x = 23 * 54;}


Ide

methodcore (_), or

m length

Sun Services


Identifiers

ntifiers have the following characteristics:

• Are names given to a variable, class, or• Can start with a Unicode letter, unders

dollar sign ($)• Are case-sensitive and have no maximu• Examples:

identifieruserNameuser_name_sys_var1$change


eywords

Re e

abs switch

ass synchronized

boo this

bre d throw

byt throws

cas transient

cat try

cha void

cla volatile

con while

Sun Services


Java Programming Language K

served literal words: null, true, and fals

tract continue for new

ert default goto package

lean do if private

ak double implements protecte

e else import public

e enum instanceof return

ch extends int short

r final interface static

ss finally long strictfp

st float native super


Th t primitivetyp

Sun Services


Primitive Types

e Java programming language defines eighes:

• Logical – boolean• Textual – char• Integral – byte, short, int, and long

• Floating – double and float


Th acteristics:

, true and

n type and

Sun Services


Logical – boolean

e boolean primitive has the following char

• The boolean data type has two literalsfalse.

• For example, the statement:boolean truth = true;

declares the variable truth as booleaassigns it a value of true.


Th characteristics:

quotes (’ ’)

is replaced with

letter phi [Φ].

Sun Services


Textual – char

e textual char primitive has the following

• Represents a 16-bit Unicode character• Must have its literal enclosed in single • Uses the following notations:

'a' The letter a

'\t' The tab character

'\u????' A specific Unicode character, ????, exactly four hexadecimal digits .For example, ’\u03A6’ is the Greek


Th aracteristics:

s (" ")

Sun Services


Textual – String

e textual String type has the following ch

• Is not a primitive data type; it is a class• Has its literal enclosed in double quote

"The quick brown fox jumps over the lazy dog."

• Can be used as follows:String greeting = "Good Morning !! \n";String errorMessage = "Record Not Found !";


d long

Th aracteristics:

mal, octal, or

long.

e.

al value.

Sun Services


Integral – byte, short, int, an

e integral primitives have the following ch

• Integral primates use three forms: Decihexadecimal

• Literals have a default type of int.

• Literals with the suffix L or l are of type

2 The decimal form for the integer 2.

077 The leading 0 indicates an octal valu

0xBAAC The leading 0x indicates a hexadecim


d long

ranges:

Sun Services


Integral – byte, short, int, an

• Integral data types have the following

Integer Length Name or Type Range

8 bits byte -27 to 27-1

16 bits short -215 to 215 -1

32 bits int -231 to 231 -1

64 bits long -263 to 263 -1


ouble

Th ngcha

ecimal point or

ouble)

dant D

Sun Services


Floating Point – floatand d

e floating point primitives have the followiracteristics:

• Floating-point literal includes either a done of the following:• E or e (add exponential value)• F or f (float)• D or d (double)

3.14 A simple floating-point value (a d

6.02E23 A large floating-point value

2.718F A simple float size value

123.4E+306D A large double value with redun


ouble

owing sizes:

Sun Services


Floating Point – floatand d

• Literals have a default type of double.• Floating-point data types have the foll

Float Length Name or Type

32 bits float

64 bits double

Sun Services

Variables, Declarations, andAssignments

1 public class Assign {2 public static void main (String args []) {3 // declare integer variables4 int x, y;5 // declare and assign floating point6 float z = 3.414f;7 // declare and assign double8 double w = 3.1415;9 // declare and assign boolean10 boolean truth = true;11 // declare character variable12 char c;13 // declare String variable14 String str;15 // declare and assign String variable16 String str1 = "bye";17 // assign value to char variable18 c = 'A';19 // assign value to String variable20 str = "Hi out there!";21 // assign values to int variables22 x = 6;23 y = 1000;24 }25 }



pes all others

n object.

r) { ... }

Sun Services


Java Reference Types

• In Java technology, beyond primitive tyare reference types.

• A reference variable contains a handle to a• For example:

1 public class MyDate {2 private int day = 1;3 private int month = 1;4 private int year = 2000;5 public MyDate(int day, int month, int yea6 public String toString() { ... }7 }

1 public class TestMyDate {2 public static void main(String[] args) {3 MyDate today = new MyDate(22, 7, 1964);4 }5 }


bjects

ing actions:

rformed.

the new

o a variable.

Sun Services


Constructing and Initializing O

• Calling new Xyz() performs the followa. Memory is allocated for the object.b. Explicit attribute initialization is pec. A constructor is executed.d. The object reference is returned by

operator.• The reference to the object is assigned t• An example is:

MyDate my_birth = new MyDate(22, 7, 1964);


out

a reference:

for MyDate:

Sun Services


Memory Allocation and Lay

• A declaration allocates storage only forMyDate my_birth = new MyDate(22, 7, 1964);

• Use the new operator to allocate space MyDate my_birth = new MyDate(22, 7, 1964);

my_birth ????

my_birth ????

day

month

year

0

0

0


ion

ttribute

Sun Services


Explicit Attribute Initializat

• Initialize the attributes as follows:MyDate my_birth = new MyDate(22, 7, 1964);

• The default values are taken from the adeclaration in the class.

my_birth ????

day

month

year

1

1

2000


or

llows:

r, the first

Sun Services


Executing the Construct

• Execute the matching constructor as foMyDate my_birth = new MyDate(22, 7, 1964);

• In the case of an overloaded constructoconstructor can call another.

my_birth ????

day

month

year

22

7

1964


eference

Sun Services


Assigning a Variable

• Assign the newly created object to the rvariable as follows:MyDate my_birth = new MyDate(22, 7, 1964);

my_birth 0x01abcdef

day

month

year

22

7

1964


nt to two

Sun Services


Assigning References

• Two variables refer to a single object:1 int x = 7;2 int y = x;3 MyDate s = new MyDate(22, 7, 1964);4 MyDate t = s;

• Reassignment makes two variables poiobjects:5 t = new MyDate(22, 12, 1964);

x 7

y 7

s 0x01234567

t 0x01234567

22 7 1964

x 7

y 7

s 0x01234567

t 0x12345678

22 7 1964

22 12 1964


ogramminglue. argument to areference to the

d in the callede is never

Sun Services


Pass-by-Value

• In a single virtual machine, the Java prlanguage only passes arguments by va

• When an object instance is passed as anmethod, the value of the argument is aobject.

• The contents of the object can be changemethod, but the original object referencchanged.


123456789101112

Sun Services


Pass-by-Value

public class PassTest {

// Methods to change the current values public static void changeInt(int value) { value = 55; } public static void changeObjectRef(MyDate ref) { ref = new MyDate(1, 1, 2000); } public static void changeObjectAttr(MyDate ref){ ref.setDay(4); }


1314151617181920212223

Th

Sun Services


Pass-by-Value

public static void main(String args[]) { MyDate date; int val;

// Assign the int val = 11; // Try to change it changeInt(val); // What is the current value? System.out.println("Int value is: " + val);

e result of this output is:

Int value is: 11


24252627282930

Th

Sun Services


Pass-by-Value

// Assign the date date = new MyDate(22, 7, 1964); // Try to change it changeObjectRef(date); // What is the current value?

System.out.println("MyDate: " + date);


MyDate: 22-7-1964


3132333435363738

Th

Sun Services


Pass-by-Value

// Now change the day attribute // through the object reference changeObjectAttr(date); // What is the current value?

System.out.println("MyDate: " + date);}

}


MyDate: 4-7-1964


He

variables and

er to another

Sun Services


The thisReference

re are a few uses of the this keyword:

• To resolve ambiguity between instanceparameters

• To pass the current object as a parametmethod or constructor


123456789101112131415

Sun Services


The thisReference

public class MyDate { private int day = 1; private int month = 1; private int year = 2000;

public MyDate(int day, int month, int year) { this.day = day; this.month = month; this.year = year; } public MyDate(MyDate date) { this.day = date.day; this.month = date.month; this.year = date.year; }


1617181920212223242526

Sun Services


The thisReference

public MyDate addDays(int moreDays) { MyDate newDate = new MyDate(this); newDate.day = newDate.day + moreDays; // Not Yet Implemented: wrap around code... return newDate; }public String toString() {

return "" + day + "-" + month + "-" + year; }}


12345678

Sun Services


The thisReference

public class TestMyDate { public static void main(String[] args) { MyDate my_birth = new MyDate(22, 7, 1964); MyDate the_next_week = my_birth.addDays(7);

System.out.println(the_next_week); }}


Coding

Sun Services


Java Programming LanguageConventions

• Packages:com.example.domain;

• Classes, interfaces, and enum types:SavingsAccount

• Methods:getAccount()

• Variables:currentCustomer

• Constants:HEAD_COUNT


Coding

on.

ss members.

Sun Services


Java Programming LanguageConventions

• Control structures:if ( condition ) {statement1;

} else {statement2;

}

• Spacing:• Use one statement per line.• Use two or four spaces for indentati

• Comments:• Use // to comment inline code.• Use /** documentation */ for cla

Sun

Java™ Programmi

ontrol

Services

ng Language

Module 4

Expressions and Flow C


variablesablesence before

are operatorsssignments of

Sun Services


Objectives

• Distinguish between instance and local• Describe how to initialize instance vari• Identify and correct a Possible refer

assignment compiler error• Recognize, describe, and use Java softw• Distinguish between legal and illegal a

primitive types


requirements

d required casts

structions andue as flow

Sun Services


Objectives

• Identify boolean expressions and theirin control constructs

• Recognize assignment compatibility anin fundamental types

• Use if, switch, for, while, and do conthe labeled forms of break and contincontrol structures in a program


ogrammers?th the same

ed in otherguages use to

Sun Services


Relevance

• What types of variables are useful to pr• Can multiple classes have variables wi

name and, if so, what is their scope?• What types of control structures are us

languages? What methods do these lancontrol flow?


Lo

od and arek variableshod is executedd

Va :

ation.atically.

Sun Services


Variables and Scope

cal variables are:

• Variables that are defined inside a methcalled local, automatic, temporary, or stac

• Variables that are created when the metare destroyed when the method is exite

riable initialization comprises the following

• Local variables require explicit initializ• Instance variables are initialized autom


epub p

p

} p

}}

pubp

}}

Heap Memory

ScopeExample

i 1

ack

Sun Services


Variable Scope Exampllic class ScopeExample {rivate int i=1;

ublic void firstMethod() { int i=4, j=5;

this.i = i + j; secondMethod(7);

ublic void secondMethod(int i) {int j=8; this.i = i + j;

lic class TestScoping {ublic static void main(String[] args) {ScopeExample scope = new ScopeExample();

scope.firstMethod();

main

firstMethod

i

j

secondMethod

i

j

this

this

scope

4

5

7

8

Execution St


Sun Services


Variable Initialization

Variable Value

byte 0

short 0

int 0

long 0L

float 0.0F

double 0.0D

char '\u0000'

boolean false

All reference types null


ciple

Th ave beenini

javTest en initialized 1 er

345678910 ation11

Sun Services


Initialization Before Use Prin

e compiler will verify that local variables htialized before used.

ac TestInitBeforeUse.javaInitBeforeUse.java:10: variable y might not have bez = y + x; // Possible use before initialization ^ror

public void doComputation() { int x = (int)(Math.random() * 100); int y; int z; if (x > 50) { y = 9; } z = y + x; // Possible use before initializ }


Op ssociative++ to L* to R+ to R<< to R< to R== to R& to R^ to R| to R&& to R|| to R<b to L= * to L

Sun Services


Operator Precedence

erators A-- + unary - unary ~ ! (<data_type>) R/ % L- L>> >>> L> <= >= instanceof L!= L

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Sun Services


Logical Operators

• The boolean operators are:! – NOT & – AND| – OR ^ – XOR

• The short-circuit boolean operators ar&& – AND || – OR

• You can use these operators as followsMyDate d = reservation.getDepartureDate();if ( (d != null) && (d.day > 31) {// do something with d

}


s

0 1

1 1

0 1

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Sun Services


Bitwise Logical Operator

• The integer bitwise operators are:~ – Complement & – AND^ – XOR | – OR

• Byte-sized examples include:

0 0 01 1 1 1 1

1 1 10 0 0 0 0

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0 0 01 1 1

0 0 01 1 1

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Sun Services


Right-Shift Operators >>and

• Arithmetic or signed right shift (>>) ope• Examples are:

128 >> 1 returns 128/21 = 64256 >> 4 returns 256/24 = 16-256 >> 4 returns -256/24 = -16

• The sign bit is copied during the shi• Logical or unsigned right-shift (>>>) ope

• This operator is used for bit patterns• The sign bit is not copied during the


s:

Sun Services


Left-Shift Operator <<

• Left-shift (<<) operator works as follow128 << 1 returns 128 * 21 = 25616 << 2 returns 16 * 22 = 64


s

0 10 0 1 1

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Sun Services


Shift Operator Example

1

1

0

0

00 0 000 0 000 0 000 0 0

11 1 1 11 1 111 1 1 11 1 1 11 1 1

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1111 00011 1 1 11 1 111 1 11 1 1

000 0 000 0 000 0 000 0 0

0 0111 0000 0 000 0 000 0 000 0

0 00 0 0

11 1 11

000 0 000 0 000 0 000 0 00 00 0 0

11 1 1 111 1 1 11 1 1 11 1 10 00 0 0


h +

.bjects

Sun Services


String Concatenation Wit

• The + operator works as follows:• Performs String concatenation• Produces a new String:

String salutation = "Dr.";String name = "Pete" + " " + "Seymour";String title = salutation + " " + name;

• One argument must be a String object• Non-strings are converted to String o

automatically.


nment, theent with a cast. requires an

a cast

a cast

ger literal

Sun Services


Casting

• If information might be lost in an assigprogrammer must confirm the assignm

• The assignment between long and intexplicit cast.long bigValue = 99L;int squashed = bigValue; // Wrong, needsint squashed = (int) bigValue; // OK

int squashed = 99L; // Wrong, needsint squashed = (int) 99L; // OK, but...int squashed = 99; // default inte


essions

o a longer form

e variable type bits) as the

l

egal

Sun Services


Promotion and Casting of Expr

• Variables are promoted automatically t(such as int to long).

• Expression is assignment-compatible if this at least as large (the same number ofexpression type.long bigval = 6; // 6 is an int type, OKint smallval = 99L; // 99L is a long, illega

double z = 12.414F; // 12.414F is float, OKfloat z1 = 12.414; // 12.414 is double, ill


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Sun Services


Simple if, elseStateme

e if statement syntax:

( <boolean_expression> )statement_or_block>

ample:

x < 10 )stem.out.println("Are you finished yet?");

(recommended):

x < 10 ) {stem.out.println("Are you finished yet?");


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Sun Services


Complex if, elseStatem

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Sun Services


Complex if, elseStatem

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( <boolean_expression> )statement_or_block>e if ( <boolean_expression> )statement_or_block>

ample:

count = getCount(); // a method defined in the clascount < 0) {stem.out.println("Error: count value is negative.")se if (count > getMaxCount()) {stem.out.println("Error: count value is too big.");se {stem.out.println("There will be " + count +

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Sun Services


Switch Statements

e switch statement syntax:

tch ( <expression> ) {ase <constant1>:<statement_or_block>*[break;]

ase <constant2>:<statement_or_block>*[break;]

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Sun Services


Switch Statements

witch statement example:

ch ( carModel ) {se DELUXE:addAirConditioning();addRadio();addWheels();addEngine();break;se STANDARD:addRadio();addWheels();addEngine();break;fault:addWheels();addEngine();


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Sun Services


Switch Statements

is switch statement is equivalent to the pre

ch ( carModel ) {se DELUXE:addAirConditioning();se STANDARD:addRadio();fault:addWheels();addEngine();

thout the break statements, the execution h subsequent case clause.


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Sun Services


Looping Statements

e for loop:

( <init_expr>; <test_expr>; <alter_expr> )statement_or_block>

ample:

( int i = 0; i < 10; i++ )stem.out.println(i + " squared is " + (i*i));

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Sun Services


Looping Statements

e while loop:

le ( <test_expr> )statement_or_block>

ample:

i = 0;e ( i < 10 ) {stem.out.println(i + " squared is " + (i*i));+;


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Sun Services


Looping Statements

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statement_or_block>le ( <test_expr> );

ample:

i = 0;

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dand, where

Sun Services


Special Loop Flow Contr

• The break [<label>]; command• The continue [<label>]; comman• The <label> : <statement> comm

<statement> should be a loop


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Sun Services


The breakStatement

do {statement;if ( condition ) {break;

}statement;

} while ( test_expr );


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Sun Services


The continueStatemen

do {statement;if ( condition ) {continue;

}statement;



Labels

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Sun Services


Using breakStatements with

outer:do {statement1;do {statement2;if ( condition ) {break outer;

}statement3;

} while ( test_expr );statement4;



th Labels

123456789101112

Sun Services


Using continueStatements wi

test:do {statement1;do {statement2;if ( condition ) {continue test;

}statement3;

} while ( test_expr );statement4;


Sun

Java™ Programmi

Services

ng Language

Module 5

Arrays


class, or array

nitializedf an arrayn array

ne array to

Sun Services


Objectives

• Declare and create arrays of primitive, types

• Explain why elements of an array are i• Explain how to initialize the elements o• Determine the number of elements in a• Create a multidimensional array• Write code to copy array values from o

another


Wh

Sun Services


Relevance

at is the purpose of an array?


es:

new.

Sun Services


Declaring Arrays

• Group data objects of the same type.• Declare arrays of primitive or class typ

char s[];Point p[];

char[] s;Point[] p;

• Create space for a reference.• An array is an object; it is created with


Us .

For

12345678910

Sun Services


Creating Arrays

e the new keyword to create an array object

example, a primitive (char) array:

public char[] createArray() {char[] s;

s = new char[26];for ( int i=0; i<26; i++ ) {s[i] = (char) (’A’ + i);

}

return s;}


C imitives

ory

Sun Services


reating an Array of Character Pr

main

createArray s

this

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A

Execution Stack

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B

C

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Sun Services


Creating Reference Arra

other example, an object array:

public Point[] createArray() {Point[] p;

p = new Point[10];for ( int i=0; i<10; i++ ) {p[i] = new Point(i, i+1);

}

return p;}


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nt

0

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Sun Services


reating an Array of Character PrWith PointObjects

main

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Poi

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Strnamnamnamnam

{

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{, 7, 1964), 1, 2000),, 12, 1964)

Sun Services


Initializing Arrays

• Initialize an array element.• Create an array with initial values.ing[] names;es = new String[3];es[0] = "Georgianna";es[1] = "Jen";es[2] = "Simon";

String[] names = "Georgianna","Jen","Simon"

};

ate[] dates;es = new MyDate[3];es[0] = new MyDate(22, 7, 1964);es[1] = new MyDate(1, 1, 2000);es[2] = new MyDate(22, 12, 1964);

MyDate[] dates = new MyDate(22new MyDate(1,new MyDate(22

};


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Sun Services


Multidimensional Arrays

rays of arrays:

][] twoDim = new int[4][];im[0] = new int[5];im[1] = new int[5];

][] twoDim = new int[][4]; // illegal


h:

Sun Services


Multidimensional Arrays

• Non-rectangular arrays of arrays:twoDim[0] = new int[2];twoDim[1] = new int[4];twoDim[2] = new int[6];twoDim[3] = new int[8];

• Array of four arrays of five integers eacint[][] twoDim = new int[4][5];


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Sun Services


Array Bounds

array subscripts begin at 0:

ic void printElements(int[] list) {r (int i = 0; i < list.length; i++) {System.out.println(list[i]);


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Sun Services


Using the Enhanced forL

a 2 Platform, Standard Edition (J2SE™) veroduced an enhanced for loop for iterating

ic void printElements(int[] list) {r ( int element : list ) {System.out.println(element);

e for loop can be read as for each element


e to refer to an

Sun Services


Array Resizing

• You cannot resize an array.• You can use the same reference variabl

entirely new array, such as:int[] myArray = new int[6];myArray = new int[10];


Th rays is:

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Sun Services


Copying Arrays

e System.arraycopy() method to copy ar

//original arrayint[] myArray = { 1, 2, 3, 4, 5, 6 };

// new larger arrayint[] hold = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 };

// copy all of the myArray array to the hold// array, starting with the 0th indexSystem.arraycopy(myArray, 0, hold, 0, myArray.lengt

Sun

Java™ Programmi

Services

ng Language

Module 6

Class Design


ding, overriding,

nd the default

d method

on and

Sun Services


Objectives

• Define inheritance, polymorphism, overloaand virtual method invocation

• Use the access modifiers protected a(package-friendly)

• Describe the concepts of constructor anoverloading

• Describe the complete object constructiinitialization operation


Ho pport objectinh

Sun Services


Relevance

w does the Java programming language sueritance?


Th

";

ls() {...}

Sun Services


Subclassing

e Employee class is shown here.

public class Employee { public String name = " public double salary; public Date birthDate;

public String getDetai}

Employee

+name : String = ""

+salary : double

+birthDate : Date

+getDetails() : String


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";

nt;

ls() {...}

Sun Services


Subclassing

e Manager class is shown here.

public class Manager { public String name = " public double salary; public Date birthDate; public String departme


Manager

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+salary : double

+birthDate : Date

+department : String



C d Manager

";

ls() {...}

ends Employee {nt;

Sun Services


lass Diagrams for EmployeeanUsing Inheritance

public class Employee { public String name = " public double salary; public Date birthDate;


public class Manager ext public String departme}

Manager

+department : String

Employee

+name : String = ""

+salary : double

+birthDate : Date



ss, it is called

le inheritance

s>] {

Sun Services


Single Inheritance

• When a class inherits from only one clasingle inheritance.

• Interfaces provide the benefits of multipwithout drawbacks.

• Syntax of a Java class is as follows:<modifier> class <name> [extends <superclas<declaration>*

}


cretary

Sun Services


Single Inheritance

Manager

+department : String = ""

Employee

+name : String = ""

+salary : double

+birthDate : Date

Director

+carAllowance : double

Engineer Se


+increaseAllowance()


Ac s are listed here.

Mo ass Universe

pri

def

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pub Yes

Sun Services


Access Control

cess modifiers on class member declaration

difier Same Class Same Package Subcl

vate Yes

ault Yes Yes

tected Yes Yes Yes

lic Yes Yes Yes


ed from a

fferent but with the

1.

Sun Services


Overriding Methods

• A subclass can modify behavior inheritparent class.

• A subclass can create a method with difunctionality than the parent’s methodsame:• Name• Return type1

• Argument list

In J2SE version 5, the return type can be a subclass of the overridden return type.


12345678910

123456789

Sun Services


Overriding Methods

public class Employee {protected String name;protected double salary;protected Date birthDate;

public String getDetails() {return “Name: “ + name + “\n” +

“Salary: “ + salary;}

}

public class Manager extends Employee {protected String department;

public String getDetails() {return “Name: “ + name + “\n” +

“Salary: “ + salary + "\n" +“Manager of: “ + department;

}}


e Less

123

123

12345678

Sun Services


Overridden Methods Cannot BAccessible

public class Parent {public void doSomething() {}

}

public class Child extends Parent {private void doSomething() {} // illegal

}

public class UseBoth {public void doOtherThing() {Parent p1 = new Parent();Parent p2 = new Child();p1.doSomething();p2.doSomething();

}}


ods

A s ethod using thesup

refer to its

the members ofthods.the superclass;

Sun Services


Invoking Overridden Meth

ubclass method may invoke a superclass mer keyword:

• The keyword super is used in a class tosuperclass.

• The keyword super is used to refer tosuperclass, both data attributes and me

• Behavior invoked does not have to be init can be further up in the hierarchy.


ods

123456789

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Sun Services


Invoking Overridden Meth

public class Employee {private String name;private double salary;private Date birthDate;

public String getDetails() {return "Name: " + name + "\nSalary: " + salary;

}}

public class Manager extends Employee {private String department;

public String getDetails() {// call parent methodreturn super.getDetails()

+ “\nDepartment: " + department;}

}


y differentas access to

of different

Sun Services


Polymorphism

• Polymorphism is the ability to have manforms; for example, the Manager class hmethods from Employee class.

• An object has only one form.• A reference variable can refer to objects

forms.


Empl

// e.de// t// e

Sun Services


Polymorphism

oyee e = new Manager(); // legal

illegal attempt to assign Manager attributepartment = "Sales";he variable is declared as an Employee type,ven though the Manager object has that attribute


n

d as follows:

vocations have

of the declared has a method

based on theManager classtails method.

Sun Services


Virtual Method Invocatio

• Virtual method invocation is performeEmployee e = new Manager();e.getDetails();

• Compile-time type and runtime type inthe following characteristics:• The method name must be a member

variable type; in this case Employeecalled getDetails.

• The method implementation used isruntime object’s type; in this case thehas an implementation of the getDe


ns

ss type areple:

ss types aremple:

Sun Services


Heterogeneous Collectio

• Collections of objects with the same clacalled homogeneous collections. For examMyDate[] dates = new MyDate[2];dates[0] = new MyDate(22, 12, 1964);dates[1] = new MyDate(22, 7, 1964);

• Collections of objects with different clacalled heterogeneous collections. For exaEmployee [] staff = new Employee[1024];staff[0] = new Manager();staff[1] = new Employee();staff[2] = new Engineer();


Bec ing is valid:

publpu

}}

// MTaxSManTaxR

Sun Services


Polymorphic Arguments

ause a Manager is an Employee, the follow

ic class TaxService {blic TaxRate findTaxRate(Employee e) {// calculate the employee’s tax rate

eanwhile, elsewhere in the application classervice taxSvc = new TaxService();ager m = new Manager();ate t = taxSvc.findTaxRate(m);


or

publpublpubl----

publif

}

}

}}

Sun Services


The instanceofOperat

ic class Employee extends Objectic class Manager extends Employeeic class Engineer extends Employee------------------------------------

ic void doSomething(Employee e) { ( e instanceof Manager ) {// Process a Managerelse if ( e instanceof Engineer ) {// Process an Engineerelse {// Process any other type of Employee


”

Sun Services


Casting Objects

public void doSomething(Employee e) {if ( e instanceof Manager ) {Manager m = (Manager) e;System.out.println(“This is the manager of

+ m.getDepartment());}// rest of operation

}


bject.y casting.wing

ne implicitly.s and checked

when runtime

Sun Services


Casting Objects

• Use instanceof to test the type of an o• Restore full functionality of an object b• Check for proper casting using the follo

guidelines:• Casts upward in the hierarchy are do• Downward casts must be to a subclas

by the compiler.• The object type is checked at runtime

errors can occur.


Sun Services


Overloading Methods

• Use overloading as follows:public void println(int i)public void println(float f)public void println(String s)

• Argument lists must differ.• Return types can be different.


ments

it multiple

array. For

););

Sun Services


Methods Using Variable Argu

• Methods using variable arguments permnumber of arguments in methods.For example:public class Statistics {public float average(int... nums) {int sum = 0;for ( int x : nums ) {sum += x;

}return ((float) sum) / nums.length;

}}

• The vararg parameter is treated as anexample:float gradePointAverage = stats.average(4, 3, 4float averageAge = stats.average(24, 32, 27, 18


rs

verloaded.

e DoB)

irst line of a

Sun Services


Overloading Constructo

• As with methods, constructors can be oAn example is:public Employee(String name, double salary, Datpublic Employee(String name, double salary)public Employee(String name, Date DoB)

• Argument lists must differ.• You can use the this reference at the f

constructor to call another constructor.


rs

12 0;34567 DoB) {8910111213141516171819

Sun Services


Overloading Constructo

public class Employee { private static final double BASE_SALARY = 15000.0 private String name; private double salary; private Date birthDate;

public Employee(String name, double salary, Date this.name = name; this.salary = salary; this.birthDate = DoB; }public Employee(String name, double salary) {

this(name, salary, null); } public Employee(String name, Date DoB) { this(name, BASE_SALARY, DoB); }// more Employee code...

}


ited

iables from the

ctor from the

ors.

Sun Services


Constructors Are Not Inher

• A subclass inherits all methods and varsuperclass (parent class).

• A subclass does not inherit the construsuperclass.

• Two ways to include a constructor are:• Use the default constructor.• Write one or more explicit construct


uctors

st place a call tor.or by theper.structor, thenper() that callshich could be

s, but does noten a compiler

Sun Services


Invoking Parent Class Constr

• To invoke a parent constructor, you musuper in the first line of the constructo

• You can call a specific parent constructarguments that you use in the call to su

• If no this or super call is used in a conthe compiler adds an implicit call to suthe parent no argument constructor (wthe default constructor).If the parent class defines constructorprovide a no-argument constructor, therror message is issued.


uctors

1234 dept) {56789101112 s: no super()13141516

Sun Services


Invoking Parent Class Constr

public class Manager extends Employee {private String department;

public Manager(String name, double salary, Stringsuper(name, salary);department = dept;

}public Manager(String name, String dept) {super(name);department = dept;

}public Manager(String dept) { // This code faildepartment = dept;

}//more Manager code...

}


C ts: A Slight

Me occurs.

Ins s recursively:

then skip to

t super call,

initializers.ructor.

Sun Services


onstructing and Initializing ObjecReprise

mory is allocated and default initialization

tance variable initialization uses these step

1. Bind constructor parameters.2. If explicit this(), call recursively, and

Step 5.3. Call recursively the implicit or explici

except for Object.4. Execute the explicit instance variable5. Execute the body of the current const

Sun Services

Constructor and InitializationExamples

1 public class Object {2 public Object() {}3 }

1 public class Employee extends Object {2 private String name;3 private double salary = 15000.00;4 private Date birthDate;56 public Employee(String n, Date DoB) {7 // implicit super();8 name = n;9 birthDate = DoB;10 }11 public Employee(String n) {12 this(n, null);13 }14 }

1 public class Manager extends Employee {2 private String department;34 public Manager(String n, String d) {5 super(n);6 department = d;7 }8 }



xamples

0 Ba 0. 0.1 C 1. 1. 1. ull

Sun Services


Constructor and Initialization E

sic initialization1 Allocate memory for the completeManager object2 Initialize all instance variables to their default values (0 ornull)

all constructor:Manager("Joe Smith", "Sales")1 Bind constructor parameters:n="Joe Smith", d="Sales"2 No explicitthis() call3 Callsuper(n) forEmployee(String)1.3.1 Bind constructor parameters:n="Joe Smith"1.3.2 Callthis(n, null) forEmployee(String, Date) 1.3.2.1 Bind constructor parameters:n="Joe Smith", DoB=n 1.3.2.2 No explicitthis() call 1.3.2.3 Callsuper() forObject() 1.3.2.3.1 No binding necessary 1.3.2.3.2 Nothis() call 1.3.2.3.3 Nosuper() call(Object is the root) 1.3.2.3.4 No explicit variable initialization forObject 1.3.2.3.5 No method body to call


xamples

0; 1. 1.

Sun Services


Constructor and Initialization E

1.3.2.4 Initialize explicit Employee variables:salary=15000.0 1.3.2.5 Execute body:name="Joe Smith"; date=null;1.3.3 - 1.3.4 Steps skipped1.3.5 Execute body: No body inEmployee(String)4 No explicit initializers forManager5 Execute body:department="Sales"


s in Java.ause implies

Sun Services


The ObjectClass

• The Object class is the root of all classe• A class declaration with no extends cl

extends Object. For example:public class Employee { ...}

is equivalent to:public class Employee extends Object { ...}

• Two important methods are:• equals

• toString


rences arehe same object).ts are equal but

als method

ethod touality.emethod if you

Sun Services


The equalsMethod

• The == operator determines if two refeidentical to each other (that is, refer to t

• The equalsmethod determines if objecnot necessarily identical.

• The Object implementation of the equuses the == operator.

• User classes can override the equals mimplement a domain-specific test for eq

• Note: You should override thehashCodoverride the equals method.


12345678910

Sun Services


An equalsExample

public class MyDate { private int day; private int month; private int year;

public MyDate(int day, int month, int year) { this.day = day; this.month = month; this.year = year; }


1112131415161718192021222324252627

Sun Services


An equalsExample

public boolean equals(Object o) {boolean result = false;if ( (o != null) && (o instanceof MyDate) ) {MyDate d = (MyDate) o;if ( (day == d.day) && (month == d.month)

&& (year == d.year) ) {result = true;

}}return result;

}

public int hashCode() {return (day ^ month ^ year);

}}


1234567 e2");89 date2");10111213 ;1415 e2");16

Sun Services


An equalsExample

class TestEquals {public static void main(String[] args) {

MyDate date1 = new MyDate(14, 3, 1976); MyDate date2 = new MyDate(14, 3, 1976);

if ( date1 == date2 ) { System.out.println("date1 is identical to dat } else { System.out.println("date1 is not identical to }

if ( date1.equals(date2) ) { System.out.println("date1 is equal to date2") } else { System.out.println("date1 is not equal to dat }


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Th

datedateset date

Sun Services


An equalsExample

System.out.println("set date2 = date1;"); date2 = date1;

if ( date1 == date2 ) { System.out.println("date1 is identical to dat } else { System.out.println("date1 is not identical to } }}

is example generates the following output:

1 is not identical to date21 is equal to date2date2 = date1;1 is identical to date2


Th acteristics:

ing.ation.ation about a

c method to

Sun Services


The toStringMethod

e toString method has the following char

• This method converts an object to a Str• Use this method during string concaten• Override this method to provide inform

user-defined object in readable format.• Use the wrapper class’s toString stati

convert primitive types to a String.


Lo

Sun Services


Wrapper Classes

ok at primitive data elements as objects.

Primitive Data Type Wrapper Class

boolean Boolean

byte Byte

char Character

short Short

int Integer

long Long

float Float

double Double


An

int Inte oxingint

Oth

int int

Sun Services


Wrapper Classes

example of a wrapper class is:

pInt = 420;ger wInt = new Integer(pInt); // this is called bp2 = wInt.intValue(); // this is called unboxing

er methods are:

x = Integer.valueOf(str).intValue();x = Integer.parseInt(str);


pes

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ject equivalent

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Sun Services


Autoboxing of Primitive Ty

toboxing has the following description:

• Conversion of primitive types to the ob• Wrapper classes not always needed• Example:

int pInt = 420;Integer wInt = pInt; // this is called autoboint p2 = wInt; // this is called autounboxin

• Language feature used most often whecollections

• Wrapped primitives also usable in arithexpressions

• Performance loss when using autoboxi

Sun

Java™ Programmi

res

Services

ng Language

Module 7

Advanced Class Featu


itializersbles

Sun Services


Objectives

• Create static variables, methods, and in• Create final classes, methods, and varia• Create and use enumerated types• Use the static import statement• Create abstract classes and methods• Create and use an interface


by all instances

om being

Sun Services


Relevance

• How can you create a constant?• How can you declare data that is shared

of a given class?• How can you keep a class or method fr

subclassed or overridden?


ier on variables,

bute or methodather than any

ass members,

Sun Services


The staticKeyword

• Thestatickeyword is used as a modifmethods, and nested classes.

• The static keyword declares the attriis associated with the class as a whole rparticular instance of that class.

• Thus static members are often called clsuch as class attributes or class methods.


Cla s of a class:

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Sun Services


Class Attributes

ss attributes are shared among all instance

public class Count {private int serialNumber;public static int counter = 0;

public Count() {counter++;serialNumber = counter;

}}

c1 : Count

Count

serialNumber=1

-serialNumber : int

+counter : int = 0

c2 : Count

serialNumber=2

«instanceOf»«instanceOf»


If t

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Sun Services


Class Attributes

he static member is public:

public class Count1 {private int serialNumber;public static int counter = 0;

public Count1() { counter++; serialNumber = counter; }}

an be accessed from outside the class with

public class OtherClass { public void incrementNumber() {

Count1.counter++; }}


You

12345678910111213

Sun Services


Class Methods

can create static methods:

public class Count2 { private int serialNumber; private static int counter = 0;

public static int getTotalCount() { return counter; }

public Count2() {counter++;

serialNumber = counter; }}


You instance of thecla

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NumbNumb

Sun Services


Class Methods

can invoke static methods without anyss to which it belongs:

public class TestCounter { public static void main(String[] args) { System.out.println("Number of counter is " + Count2.getTotalCount()); Count2 counter = new Count2(); System.out.println("Number of counter is " + Count2.getTotalCount()); }}

e output of the TestCounter program is:

er of counter is 0er of counter is 1


Sta es:

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Sun Services


Class Methods

tic methods cannot access instance variabl

public class Count3 { private int serialNumber; private static int counter = 0;

public static int getSerialNumber() { return serialNumber; // COMPILER ERROR! }}


that does not

hen the class is

ze static (class)

Sun Services


Static Initializers

• A class can contain code in a static blockexist within a method body.

• Static block code executes once only, wloaded.

• Usually, a static block is used to initialiattributes.


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Sun Services


Static Initializers

public class Count4 { public static int counter;static {

counter = Integer.getInteger("myApp.Count4.coun}

}

public class TestStaticInit { public static void main(String[] args) { System.out.println("counter = "+ Count4.counter }}

e output of the TestStaticInit program

-DmyApp.Count4.counter=47 TestStaticInitter = 47


, but thatthe declaration;

t be set in every

be set in the

Sun Services


The finalKeyword

• You cannot subclass a final class.• You cannot override a final method.• A final variable is a constant.• You can set a final variable once only

assignment can occur independently ofthis is called a blank final variable.• A blank final instance attribute mus

constructor.• A blank final method variable must

method body before being used.


Co

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}

Sun Services


Final Variables

nstants are static final variables.

ic class Bank {ivate static final double DEFAULT_INTEREST_RATE = . // more declarations


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Sun Services


Blank Final Variables

public class Customer {

private final long customerID;

public Customer() {customerID = createID();

}

public long getID() {return customerID;

}

private long createID() {return ... // generate new ID

}

// more declarations

}


Idiom

En gramming.1234567891011121314151617

Sun Services


Old-Style Enumerated Type

umerated types are a common idiom in pro0

package cards.domain;

public class PlayingCard {

// pseudo enumerated type public static final int SUIT_SPADES = 0; public static final int SUIT_HEARTS = 1; public static final int SUIT_CLUBS = 2; public static final int SUIT_DIAMONDS = 3;

private int suit; private int rank;

public PlayingCard(int suit, int rank) { this.suit = suit; this.rank = rank; }


Idiom2223242526272829303132333435363738394041

Sun Services


Old-Style Enumerated Type} public String getSuitName() { String name = ““; switch ( suit ) { case SUIT_SPADES: name = “Spades”; break; case SUIT_HEARTS: name = “Hearts”; break; case SUIT_CLUBS: name = “Clubs”; break; case SUIT_DIAMONDS: name = “Diamonds”; break; default: System.err.println(“Invalid suit.”); } return name; }


Idiom

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Sun Services



-style idiom is not type-safe:0

package cards.tests;

import cards.domain.PlayingCard;

public class TestPlayingCard { public static void main(String[] args) {

PlayingCard card1 = new PlayingCard(PlayingCard.SUIT_SPADES, 2) System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuitName

// You can create a playing card with a bogus s PlayingCard card2 = new PlayingCard(47, 2); System.out.println(“card2 is the “ + card2.getR + “ of “ + card2.getSuitName }}


Idiom

Th lems:

Sun Services



is enumerated type idiom has several prob

• Not type-safe• No namespace• Brittle character• Uninformative printed values


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No es:12345678

Sun Services


The New Enumerated Ty

w you can create type-safe enumerated typ0


public enum Suit { SPADES, HEARTS, CLUBS, DIAMONDS}


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Sun Services



ing enumerated types is easy:0


public class PlayingCard {

private Suit suit; private int rank;

public PlayingCard(Suit suit, int rank) { this.suit = suit; this.rank = rank; }

public Suit getSuit() { return suit; }


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Sun Services


The New Enumerated Typ public String getSuitName() { String name = ““; switch ( suit ) { case SPADES: name = “Spades”; break; case HEARTS: name = “Hearts”; break; case CLUBS: name = “Clubs”; break; case DIAMONDS: name = “Diamonds”; break; default: // No need for error checking as the Suit // enum is finite. } return name; }


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Sun Services



umerated types are type-safe:0


import cards.domain.PlayingCard;import cards.domain.Suit;


PlayingCard card1 = new PlayingCard(Suit.SPADES, 2); System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuitName

// PlayingCard card2 = new PlayingCard(47, 2); // This will not compile. }}


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Sun Services


Advanced Enumerated Ty

umerated types can have attributes and me0


public enum Suit { SPADES (“Spades”), HEARTS (“Hearts”), CLUBS (“Clubs”), DIAMONDS (“Diamonds”);

private final String name;

private Suit(String name) { this.name = name; }

public String getName() { return name; }}


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Sun Services


Advanced Enumerated Ty

blic methods on enumerated types are acce0


import cards.domain.PlayingCard;import cards.domain.Suit;


PlayingCard card1 = new PlayingCard(Suit.SPADES, 2); System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuit().g

// NewPlayingCard card2 = new NewPlayingCard(47 // This will not compile. }}


ers from a class:er_name>;

idually or

nstants:;

Sun Services


Static Imports

• A static import imports the static membimport static <pkg_list>.<class_name>.<membORimport static <pkg_list>.<class_name>.*;

• A static import imports members indivcollectively:import static cards.domain.Suit.SPADES;ORimport static cards.domain.Suit.*;

• There is no need to qualify the static coPlayingCard card1 = new PlayingCard(SPADES, 2)

• Use this feature sparingly.


An12345678910 ank()11 etName());1213 , 2);141516

Sun Services


Static Imports

example of a static import is:0


import cards.domain.PlayingCard;import static cards.domain.Suit.*;


PlayingCard card1 = new PlayingCard(SPADES, 2); System.out.println(“card1 is the “ + card1.getR + “ of “ + card1.getSuit().g

// NewPlayingCard card2 = new NewPlayingCard(47 // This will not compile. }}


Th this:

hicle

RiverBarge

Sun Services


Abstract Classes

e design of the Shipping system looks like

Ve

Truck

Companyfleet

0..*

shipping

domainShippingMain «Uses»

FuelNeedsReport «Uses»

reports


Fle

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Sun Services


Abstract Classes

et initialization code is shown here:

public class ShippingMain {public static void main(String[] args) {Company c = new Company();

// populate the company with a fleet of vehiclec.addVehicle( new Truck(10000.0) );c.addVehicle( new Truck(15000.0) );c.addVehicle( new RiverBarge(500000.0) );c.addVehicle( new Truck(9500.0) );c.addVehicle( new RiverBarge(750000.0) );

FuelNeedsReport report = new FuelNeedsReport(c)report.generateText(System.out);

}}


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Sun Services


Abstract Classes

public class FuelNeedsReport {private Company company;

public FuelNeedsReport(Company company) {this.company = company;

}

public void generateText(PrintStream output) {Vehicle1 v;double fuel;double total_fuel = 0.0;

for ( int i = 0; i < company.getFleetSize(); i+v = company.getVehicle(i);


1617 fficency();1819 eeds "20212223 uel + " liters.");2425

Sun Services


Abstract Classes

// Calculate the fuel needed for this tripfuel = v.calcTripDistance() / v.calcFuelE

output.println("Vehicle " + v.getName() + " n+ fuel + " liters of fuel.");

total_fuel += fuel;}output.println("Total fuel needs is " + total_f

}}


An hich the fullim by the concretesub

e

() : double

: double

: double)

Sun Services


The Solution

abstract class models a class of objects in wplementation is not known but is suppliedclasses.

RiverBarg

Vehicle

+calcFuelEfficiency() : double

+calcTripDistance() : double

Truck

+calcFuelEfficiency() : double

+calcTripDistance() : double

+Truck(maxLoad : double)

{abstract}

«constructors»

«methods»+calcFuelEfficiency

+calcTripDistance()

+RiverBarge(maxLoad

«constructors»

«methods»


Th

1234

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Sun Services


The Solution

e declaration of the Vehicle class is:

public abstract class Vehicle {public abstract double calcFuelEfficiency();public abstract double calcTripDistance();

}

e Truck class must create an implementatio

public class Truck extends Vehicle {public Truck(double maxLoad) {...}

public double calcFuelEfficiency() { /* calculate the fuel consumption of a truck at } public double calcTripDistance() { /* calculate the distance of this trip on highw }}


Lik nim

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Sun Services


The Solution

ewise, the RiverBarge class must create aplementation:

public class RiverBarge extends Vehicle {public RiverBarge(double maxLoad) {...}

public double calcFuelEfficiency() { /* calculate the fuel efficiency of a river bar } public double calcTripDistance() { /* calculate the distance of this trip along th }}


lient code and.such a contractentation.

the same

interfaces.

s>]face>]* ] {

Sun Services


Interfaces

• A public interface is a contract between cthe class that implements that interface

• A Java interface is a formal declaration ofin which all methods contain no implem

• Many unrelated classes can implementinterface.

• A class can implement many unrelated• Syntax of a Java class is as follows:

<modifier> class <name> [extends <superclas[implements <interface> [,<inter

<member_declaration>*}


publpupupu

}

Sun Services


The Flyer Example

ic interface Flyer {blic void takeOff();blic void land();blic void fly();

+takeOff()

+land()

+fly()

«interface»

Flyer

+takeOff()

+land()

+fly()

Airplane


publpu

}pu

}pu

}}

Sun Services


The Flyer Example

ic class Airplane implements Flyer {blic void takeOff() {// accelerate until lift-off// raise landing gear

blic void land() {// lower landing gear// decelerate and lower flaps until touch-down// apply brakes

blic void fly() {// keep those engines running


)

an

ding()

et()

Sun Services


The Flyer Example

+takeOff()

+land()

+fly()

«interface»

Flyer

+takeOff()

+land()

+fly()

Airplane

+takeOff()

+land()

+fly()

Bird

+takeOff(

+land()

+fly()

Superm

+buildNest()

+layEggs()

+leapBuil

+stopBull


Kryptonian

eOff()

d()

()

perman

pBuilding()

pBullet()

()

Sun Services


The Flyer Example

Vehicle

Animal

+eat()

+takeOff()

+land()

+fly()

«interface»

Flyer

+takeOff()

+land()

+fly()

Airplane

+takeOff()

+land()

+fly()

Bird

+tak

+lan

+fly

Su

+buildNest()

+layEggs()

+lea

+sto

+eat() +eat


publpu */ }pu */ }pu */ }pu */ }pu */ }pu */ }

}

Sun Services


The Flyer Example

ic class Bird extends Animal implements Flyer {blic void takeOff() { /* take-off implementationblic void land() { /* landing implementationblic void fly() { /* fly implementationblic void buildNest() { /* nest building behaviorblic void layEggs() { /* egg laying behaviorblic void eat() { /* override eating behavior


Kryptonian

takeOff()

land()

fly()

Superman

leapBuilding()

stopBullet()

eat()

Sun Services


The Flyer Example

Vehicle

Animal

+eat()

+takeOff()

+land()

+fly()

«interface»

Flyer

+takeOff()

+land()

+fly()

Airplane

+takeOff()

+land()

+fly()

Bird

+

+

+

+buildNest()

+layEggs()

+

+

+eat() +

HelicopterSeaPlane


publpu

}

pr

}}

Sun Services


The Flyer Example

ic class Airport {blic static void main(String[] args) {Airport metropolisAirport = new Airport();Helicopter copter = new Helicopter();SeaPlane sPlane = new SeaPlane();

metropolisAirport.givePermissionToLand(copter);metropolisAirport.givePermissionToLand(sPlane);

ivate void givePermissionToLand(Flyer f) {f.land();


le

keOff()

nd()

y()

interface»

Flyer

ff()

)

lane

Helicopter

Sun Services


Multiple Interface Examp

+ta

+la

+fl

«

+takeO

+land(

+fly()

Airp

+dock()

+cruise()

«interface»

Sailer

SeaPlane

+dock()

+cruise()

Vehicle

RiverBarge

+dock()

+cruise()


le

publpu

}

pr

}}

Sun Services


Multiple Interface Examp

ic class Harbor {blic static void main(String[] args) {Harbor bostonHarbor = new Harbor();RiverBarge barge = new RiverBarge();SeaPlane sPlane = new SeaPlane();

bostonHarbor.givePermissionToDock(barge);bostonHarbor.givePermissionToDock(sPlane);

ivate void givePermissionToDock(Sailer s) {s.dock();


Int

sses are

interfacee classed classes

laring a class

Sun Services


Uses of Interfaces

erface uses include the following:

• Declaring methods that one or more claexpected to implement

• Determining an object’s programming without revealing the actual body of th

• Capturing similarities between unrelatwithout forcing a class relationship

• Simulating multiple inheritance by decthat implements several interfaces

Sun

Java™ Programmi

ons

Services

ng Language

Module 8

Exceptions and Asserti


ts

exceptions

iate uses of

Sun Services


Objectives

• Define exceptions• Use try, catch, and finally statemen• Describe exception categories• Identify common exceptions• Develop programs to handle your own• Use assertions• Distinguish appropriate and inappropr

assertions• Enable assertions at runtime


do you resolve

y your codeng, what might

pend CPU programs?

Sun Services


Relevance

• In most programming languages, how runtime errors?

• If you make assumptions about the waworks, and those assumptions are wrohappen?

• Is it always necessary or desirable to expower testing assertions in production


ns

ns – Illegaloundming here from code atn at all.

Sun Services


Exceptions and Assertio

• Exceptions handle unexpected situatioargument, network failure, or file not f

• Assertions document and test programassumptions – This can never be negative

• Assertion tests can be removed entirelyruntime, so the code is not slowed dow


orrect program

on class.ted as fatal or bugs are

Error class.

exceptions that

Sun Services


Exceptions

• Conditions that can readily occur in a care checked exceptions.These are represented by the Excepti

• Severe problems that normally are treasituations that probably reflect programunchecked exceptions.Fatal situations are represented by theProbable bugs are represented by theRuntimeException class.

• The API documentation shows checkedcan be thrown from a method.


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javExce r input string: "two"

matException.java:48)

Sun Services


Exception Example

public class AddArguments { public static void main(String args[]) { int sum = 0; for ( String arg : args ) { sum += Integer.parseInt(arg); } System.out.println("Sum = " + sum); }}

a AddArguments 1 2 3 4= 10

a AddArguments 1 two 3.0 4ption in thread "main" java.lang.NumberFormatException: Foat java.lang.NumberFormatException.forInputString(NumberForat java.lang.Integer.parseInt(Integer.java:447)at java.lang.Integer.parseInt(Integer.java:497)at AddArguments.main(AddArguments.java:5)


nt

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javOne

Sun Services


The try-catchStateme

public class AddArguments2 { public static void main(String args[]) {

try { int sum = 0;

for ( String arg : args ) {sum += Integer.parseInt(arg);

} System.out.println("Sum = " + sum);

} catch (NumberFormatException nfe) { System.err.println("One of the command-line "

+ "arguments is not an int}

}}

a AddArguments2 1 two 3.0 4of the command-line arguments is not an integer.


nt

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jav[two sum.[3.0 sum.Sum

Sun Services



public class AddArguments3 { public static void main(String args[]) { int sum = 0;

for ( String arg : args ) {try {sum += Integer.parseInt(arg);

} catch (NumberFormatException nfe) {System.err.println("[" + arg + "] is not an

+ " and will not be incl}

} System.out.println("Sum = " + sum); }}

a AddArguments3 1 two 3.0 4] is not an integer and will not be included in the] is not an integer and will not be included in the= 5


nt

A t h clauses:

try //

} ca// wn

} ca// thrown

} ca//

}

Sun Services



ry-catch statement can use multiple catc

{ code that might throw one or more exceptions

tch (MyException e1) { code to execute if a MyException exception is thro

tch (MyOtherException e2) { code to execute if a MyOtherException exception is

tch (Exception e3) { code to execute if any other exception is thrown


rent try-catchethod.thod and is not

ed abnormally.

Sun Services


Call Stack Mechanism

• If an exception is not handled in the curblock, it is thrown to the caller of that m

• If the exception gets back to the main mehandled there, the program is terminat


Th at alwaysexe

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Sun Services


The finallyClause

e finally clause defines a block of code thcutes.

try { startFaucet(); waterLawn();} catch (BrokenPipeException e) {

logProblem(e); } finally { stopFaucet();}


icException

terException

rgumentException

ception

rflowError

oryError

Sun Services


Exception Categories

Throwable

Error

Exception

RuntimeException

IOException

Arithmet

NullPoin

IllegalA

FileNotFoundEx

VirtualMachineError

AssertionError

StackOve

OutOfMem

EOFException

SQLException


Sun Services


Common Exceptions

• NullPointerException

• FileNotFoundException

• NumberFormatException

• ArithmeticException

• SecurityException


le

Us

on by using the

on { ... }

Oth

eptions or

ptions.

Sun Services


The Handle or Declare Ru

e the handle or declare rule as follows:

• Handle the exception by using thetry-catch-finally block.

• Declare that the code causes an exceptithrows clause.void trouble() throws IOException { ... }void trouble() throws IOException, MyExcepti

er Principles

• You do not need to declare runtime excerrors.

• You can choose to handle runtime exce


ptions

Th

by the

s thrown by the

Th

e overridden

by the

Sun Services


Method Overriding and Exce

e overriding method can throw:

• No exceptions• One or more of the exceptions thrown

overridden method• One or more subclasses of the exception

overridden method

e overriding method cannot throw:

• Additional exceptions not thrown by thmethod

• Superclasses of the exceptions thrown overridden method


tions

12345

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Sun Services


Method Overriding and Excep

public class TestA { public void methodA() throws IOException { // do some file manipulation }}

public class TestB1 extends TestA { public void methodA() throws EOFException {

// do some file manipulation}

}

public class TestB2 extends TestA { public void methodA() throws Exception { // WRON

// do some file manipulation}

}


ions

1 ception {234 t port) {56789101112

Us the Exceptioncla n was made.

Sun Services


Creating Your Own Except

public class ServerTimedOutException extends Ex private int port;

public ServerTimedOutException(String message, insuper(message);

this.port = port; }

public int getPort() { return port; }}

e the getMessage method, inherited from ss, to get the reason for which the exceptio


eption

A m exception:

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Sun Services


Handling a User-Defined Exc

ethod can throw a user-defined, checked

public void connectMe(String serverName)throws ServerTimedOutException {

boolean successful; int portToConnect = 80;

successful = open(serverName, portToConnect);

if ( ! successful ) {throw new ServerTimedOutException("Could no portToCon

}}


eption

An o captureuse

12345 alternative");6789 e() +10 e1.getPort());111213

Sun Services


Handling a User-Defined Exc

other method can use a try-catch block tr-defined exceptions:

public void findServer() { try { connectMe(defaultServer); } catch (ServerTimedOutException e) { System.out.println("Server timed out, trying try { connectMe(alternativeServer); } catch (ServerTimedOutException e1) { System.out.println("Error: " + e1.getMessag " connecting to port " + } } }


ssion> ;

false, then an

string and usedror message.

Sun Services


Assertions

• Syntax of an assertion is:assert <boolean_expression> ;assert <boolean_expression> : <detail_expre

• If <boolean_expression> evaluatesAssertionError is thrown.

• The second argument is converted to aas descriptive text in the AssertionEr


rtions

Us umptions andint

Ina

meters of a

eck that can

Sun Services


Recommended Uses of Asse

e assertions to document and verify the assernal logic of a single method:

• Internal invariants• Control flow invariants• Postconditions and class invariants

ppropriate Uses of Assertions

• Do not use assertions to check the parapublic method.

• Do not use methods in the assertion chcause side-effects.


Th

12345

Th

123456

Sun Services


Internal Invariants

e problem is:

if (x > 0) {// do this

} else {// do that

}

e solution is:

if (x > 0) {// do this

} else {assert ( x == 0 );// do that, unless x is negative

}


For

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Sun Services


Control Flow Invariants

example:

switch (suit) { case Suit.CLUBS: // ... break; case Suit.DIAMONDS: // ... break; case Suit.HEARTS: // ... break; case Suit.SPADES: // ... break; default: assert false : "Unknown playing car break;}


riants

For

1234 empty stack");567 ement */ ;8910111213

Sun Services


Postconditions and Class Inva

example:

public Object pop() { int size = this.getElementCount(); if (size == 0) { throw new RuntimeException("Attempt to pop from }

Object result = /* code to retrieve the popped el

// test the postconditionassert (this.getElementCount() == size - 1);

return result;}


C Assertions

e runs as fast as

lt. Enables:

class, package,

Sun Services


ontrolling Runtime Evaluation of

• If assertion checking is disabled, the codif the check was never there.

• Assertion checks are disabled by defauassertions with the following commandjava -enableassertions MyProgram

or:java -ea MyProgram

• Assertion checking can be controlled onand package hierarchy bases, see:docs/guide/language/assert.html

Sun

Java™ Programmi

ns

Services

ng Language

Module 9

Text-Based Applicatio


ne arguments

rd inputd outputnd write filesns in the Java 2)

tionctions

Sun Services


Objectives

• Write a program that uses command-liand system properties

• Write a program that reads from standa• Describe the C-type formatted input an• Write a program that can create, read, a• Describe the basic hierarchy of collectio

Software Development Kit (Java 2 SDK• Write a program that uses sets and lists• Write a program to iterate over a collec• Write a program that uses generic colle


of a programnames or the

be coded to

collections (thatava technologyollections?ents of any

Sun Services


Relevance

• It is often the case that certain elementsshould not be hard-coded, such as file name of a database. How can a programsupply these elements at runtime?

• Simple arrays are far too static for mostis, a fixed number of elements). What Jfeatures exist to support more flexible c

• Besides computation, what are key elemtext-based application?


ts

se

he commandthe class name:

in the argsethod:

Sun Services


Command-Line Argumen

• Any Java technology application can ucommand-line arguments.

• These string arguments are placed on tline to launch the Java interpreter, afterjava TestArgs arg1 arg2 "another arg"

• Each command-line argument is placedarray that is passed to the static main mpublic static void main(String[] args)


s

1234 rgs[i] + "’");567

Ex

javargsargsargs

Sun Services


Command-Line Argument

public class TestArgs { public static void main(String[] args) { for ( int i = 0; i < args.length; i++ ) { System.out.println("args[" + i + "] is ’" + a } }}

ample execution:

a TestArgs arg1 arg2 "another arg"[0] is ’arg1’[1] is ’arg2’[2] is ’another arg’


laces the are

eturns a

ringoperty.perty.

Sun Services


System Properties

• System properties are a feature that repconcept of environment variables (whichplatform-specific).

• The System.getProperties method rProperties object.

• The getProperty method returns a Strepresenting the value of the named pr

• Use the -D option to include a new pro


pping of names

Enumeration

ringoperty.s collection into

Sun Services


The PropertiesClass

• ThePropertiesclass implements a mato values (a String to String map).

• The propertyNames method returns anof all property names.

• The getProperty method returns a Strepresenting the value of the named pr

• You can also read and write a propertiea file using load and store.


12345678910 ent();11 ;1213 ");141516

Sun Services


The PropertiesClass

import java.util.Properties;import java.util.Enumeration;

public class TestProperties { public static void main(String[] args) { Properties props = System.getProperties(); Enumeration propNames = props.propertyNames();

while ( propNames.hasMoreElements() ) { String propName = (String) propNames.nextElem String property = props.getProperty(propName) System.out.println("property ’" + propName

+ "’ is ’" + property + "’ } }}


He

jav

He

propproppropproppropprop ms Inc.’proppropprop

Sun Services


The PropertiesClass

re is an example test run of this program:

a -DmyProp=theValue TestProperties

re is the (partial) output:

erty ’java.version’ is ’1.5.0-rc’erty ’java.compiler’ is ’NONE’erty ’path.separator’ is ’:’erty ’file.separator’ is ’/’erty ’user.home’ is ’/home/basham’erty ’java.specification.vendor’ is ’Sun Microsysteerty ’user.language’ is ’en’erty ’user.name’ is ’basham’erty ’myProp’ is ’theValue’


o write to

read from

o write to

Sun Services


Console I/O

• The variable System.out enables you tstandard output.It is an object of type PrintStream.

• The variable System.in enables you tostandard input.It is an object of type InputStream.

• The variable System.err enables you tstandard error.It is an object of type PrintStream.


ut

ent and a

t without a

verloaded fornt, long,ject, and

ect) methodsent.

Sun Services


Writing to Standard Outp

• The println methods print the argumnewline character (\n).

• The print methods print the argumennewline character.

• The print and println methods are omost primitive types (boolean, char, ifloat, and double) and for char[], ObString.

• The print(Object) and println(Objcall the toString method on the argum


put

123456789101112 +13 xit");

Sun Services


Reading From Standard In

import java.io.*;

public class KeyboardInput {public static void main (String args[]) {String s;// Create a buffered reader to read// each line from the keyboard.InputStreamReader ir= new InputStreamReader(System.in);

BufferedReader in = new BufferedReader(ir);

System.out.println("Unix: Type ctrl-d to exit.""\nWindows: Type ctrl-z to e


ut

1415 reen.161718192021222324 tions.25262728

Sun Services


Reading From Standard Inp

try {// Read each input line and echo it to the scs = in.readLine();while ( s != null ) {System.out.println("Read: " + s);s = in.readLine();

}

// Close the buffered reader.in.close();

} catch (IOException e) { // Catch any IO excepe.printStackTrace();

}}

}


t

y as follows

l);

this table.

Co

%s ling the

%d cimal value.

%f es scientific

%n .

%%

Sun Services


Simple Formatted Outpu

• You can use the formatting functionalitout.printf(“name count\n”);String s = String.format(“%s %5d%n”, user, tota

• Common formatting codes are listed in

de Description

Formats the argument as a string, usually by caltoString method on the object.

%o %x Formats an integer, as a decimal, octal, or hexade

%g Formats a floating point number. The %g code usnotation.

Inserts a newline character to the string or stream

Inserts the % character to the string or stream.


t

input function.ut streams as

m);

ue);

Sun Services


Simple Formatted Inpu

• The Scanner API provides a formatted • A Scanner can be used with console inp

well as file or network streams.• You can read console input as follows:

1 import java.io.*;2 import java.util.Scanner;3 public class ScanTest {4 public static void main(String [] args) {5 Scanner s = new Scanner(System.in);6 String param = s.next();7 System.out.println("the param 1" + para8 int value = s.nextInt();9 System.out.println("second param" + val10 s.close();11 }12 }


Th ollowing:

Sun Services


Files and File I/O

e java.io package enables you to do the f

• Create File objects• Manipulate File objects• Read and write to file streams


ect

Th

;

file.txt");

Dir e File classsup les in thedir

Sun Services


Creating a New FileObj

e File class provides several utilities:

• File myFile;

• myFile = new File("myfile.txt")

• myFile = new File("MyDocs", "my

ectories are treated just like files in Java; thports methods for retrieving an array of fi

ectory, as follows:

File myDir = new File("MyDocs");myFile = new File(myDir, "myfile.txt");


es

Sun Services


The FileTests and Utiliti

• File information:String getName()String getPath()String getAbsolutePath()String getParent()long lastModified()long length()

• File modification:boolean renameTo(File newName)boolean delete()

• Directory utilities:boolean mkdir()String[] list()


s

Sun Services


The FileTests and Utilitie

• File tests:boolean exists()boolean canWrite()boolean canRead()boolean isFile()boolean isDirectory()boolean isAbsolute();


aracters.e the readLine

haracters.e print and

Sun Services


File Stream I/O

• For file input:• Use the FileReader class to read ch• Use the BufferedReader class to us

method.• For file output:

• Use the FileWriter class to write c• Use the PrintWriter class to use th

println methods.


A fi

12345678910111213

Sun Services


File Stream I/O

le input example is:

import java.io.*;public class ReadFile { public static void main (String[] args) { // Create file File file = new File(args[0]);

try { // Create a buffered reader

// to read each line from a file. BufferedReader in

= new BufferedReader(new FileReader(file)); String s;


14 o the screen.1516171819202122232425 ;26272829303132

Sun Services


File Stream I/O

// Read each line from the file and echo it ts = in.readLine();

while ( s != null ) {System.out.println("Read: " + s);s = in.readLine();

}// Close the buffered readerin.close();

} catch (FileNotFoundException e1) {// If this file does not exist

System.err.println("File not found: " + file)

} catch (IOException e2) {// Catch any other IO exceptions.

e2.printStackTrace();}

}}


123456789 from standard in.1011121314151617

Sun Services


File Output Example

import java.io.*;

public class WriteFile {public static void main (String[] args) {// Create fileFile file = new File(args[0]);

try {// Create a buffered reader to read each lineInputStreamReader isr= new InputStreamReader(System.in);

BufferedReader in = new BufferedReader(isr); // Create a print writer on this file. PrintWriter out = new PrintWriter(new FileWriter(file)); String s;


1819202122 reen.2324252627 nt writer.282930313233343536

Sun Services


File Output Example

System.out.print("Enter file text. "); System.out.println("[Type ctrl-d to stop.]");

// Read each input line and echo it to the sc while ((s = in.readLine()) != null) { out.println(s); }

// Close the buffered reader and the file pri in.close(); out.close();

} catch (IOException e) { // Catch any IO exceptions. e.printStackTrace(); } }}


g a group of

that group

lled elements; allowance ofmentationuplicates are

ates are

Sun Services


The Collections API

• A collection is a single object representinobjects known as its elements.

• The Collections API contains interfacesobjects as one of the following:• Collection – A group of objects ca

any specific ordering (or lack of) andduplicates is specified by each imple

• Set – An unordered collection; no dpermitted

• List – An ordered collection; duplicpermitted


st

Object)t

ject) intor

Sun Services


The Collections API

Collection«interface»

Set«interface»

List«interface»

HashSet

ArrayList LinkedLi

+add(element : Object) : boolean

+size() : int+remove(element : Object) : boolean

+isEmpty() : boolean+contains(element : Object) : boolean+iterator() : Iterator

+add(index : int, element :

+get(index : int) : Object+remove(index : int) : Objec

+set(index : int, element Ob+indexOf(element : Object) :+listIterator() : ListIterat


1234567891011 dded12 dded131415

Th

[one

Sun Services


A SetExample

import java.util.*;

public class SetExample { public static void main(String[] args) { Set set = new HashSet(); set.add("one"); set.add("second"); set.add("3rd"); set.add(new Integer(4)); set.add(new Float(5.0F)); set.add("second"); // duplicate, not a set.add(new Integer(4)); // duplicate, not a System.out.println(set); }}

e output generated from this program is:

, second, 5.0, 3rd, 4]


1234567891011 dded12 dded131415

Th

[one

Sun Services


A ListExample

import java.util.*

public class ListExample { public static void main(String[] args) { List list = new ArrayList(); list.add("one"); list.add("second"); list.add("3rd"); list.add(new Integer(4)); list.add(new Float(5.0F)); list.add("second"); // duplicate, is a list.add(new Integer(4)); // duplicate, is a System.out.println(list); }}

e output generated from this program is:

, second, 3rd, 4, 5.0, second, 4]


n 1.1

Co ™) include:

interface. and supports

ap interface.n on the

ementsble.

heavy weight.

Sun Services


Collections in JDK™ Versio

llections in the Java Development Kit (JDK

• The class Vector implements the List• The class Stack is a subclass of Vector

the push, pop, and peek methods.• The class Hashtable implements the M• The Enumeration interface is a variatio

Iterator interface.An enumeration is returned by the elmethod in Vector, Stack, and Hashta

• Classes are thread-safe, and therefore,• These classes also support generics.


Ge

Be

Arralistint

Aft

Arralistint

Sun Services


Generics

nerics are described as follows:

• Provides compile-time type safety• Eliminates the need for casts

fore Generics

yList list = new ArrayList();.add(0, new Integer(42));total = ((Integer)list.get(0)).intValue();

er Generics

yList<Integer> list = new ArrayList<Integer>();.add(0, new Integer(42));total = list.get(0).intValue();


I

t<E>

E)

or<E>

Sun Services


Generic Collections APCollection<E>

«interface»

Set<E>«interface»

List<E>«interface»

HashSet<E>

ArrayList<E> LinkedLis

+add(element : E) : boolean

+size() : int+remove(element : E) : boolean

+isEmpty() : boolean+contains(element : E) : boolean+iterator() : Iterator<E>

+add(index : int, element :

+get(index : int) : E+remove(index : int) : E

+set(index : int, element E)+indexOf(element : E) : int+listIterator() : ListIterat


javaNote rations.Note

javaGene call to add(int,E)as a 1 wa

12345678

Sun Services


Compiler Warnings

c GenericsWarning.java: GenericsWarning.java uses unchecked or unsafe ope: Recompile with -Xlint:unchecked for details.

c -Xlint:unchecked GenericsWarning.javaricsWarning.java:7: warning: [unchecked] unchecked member of the raw type java.util.ArrayListlist.add(0, new Integer(42)); ^rning

0

import java.util.*;public class GenericsWarning { public static void main(String[] args) { List list = new ArrayList(); list.add(0, new Integer(42)); int total = ((Integer)list.get(0)).intValue(); }}


ry element in a

ned forwards (using the

List// aIterwhilSy

}

Sun Services


Iterators

• Iteration is the process of retrieving evecollection.

• An Iterator of a Set is unordered.• A ListIterator of a List can be scan

(using the next method) or backwardsprevious method).

list = new ArrayList();dd some elementsator elements = list.iterator();e ( elements.hasNext() ) {stem.out.println(elements.next());


rchy

Sun Services


The Iterator Interface Hiera

Iterator<E>«interface»

ListIterator<E>«interface»

+hasNext() : boolean+next() : E+remove()

+hasPrevious() : boolean+previous() : E+add(element : E)+set(element : E)


Th racteristics:

Ite

loop. to go wrong.

Sun Services


Enhanced forLoop

e enhanced for loop has the following cha

• Simplified iteration over collections• Much shorter, clearer, and safer• Effective for arrays• Simpler when using nested loops• Iterator disadvantages removed

rators are error prone:

• Iterator variables occur three times per• This provides the opportunity for code


An

.hasNext() ; ){

:

Sun Services


Enhanced forLoop

enhanced for loop can look like this:

• Using iterators:public void deleteAll(Collection<NameList> c){for ( Iterator<NameList> i = c.iterator() ; iNameList nl = i.next();nl.deleteItem();

}}

• Using enhanced for loop in collectionspublic void deleteAll(Collection<NameList> c){for ( NameList nl : c ){nl.deleteItem();

}}


ps:

();

Sun Services


Enhanced forLoop

• Using enhanced for loop in arrays:public int sum(int[] array){int result = 0;for ( int element : array ) {result += element;

}return result;

}

• Using enhanced for loop in nested looList<Subject> subjects=...;List<Teacher> teachers=...;List<Course> courseList = new ArrayList<Course>for ( Subject subj : subjects ) {for ( Teacher tchr : teachers ) {courseList.add(new Course(subj, tchr));

}}

Sun

Java™ Programmi

Services

ng Language

Module 10

Building Java GUIs


AWT)package

, and layouttogether to

nd GridLayout layout

propriatelysted containers

Sun Services


Objectives

• Describe the Abstract Window Toolkit (and its components

• Define the terms containers, componentsmanagers, and describe how they work build a GUI

• Use layout managers• Use the FlowLayout, BorderLayout, a

managers to achieve a desired dynamic• Add components to a container• Use the Frame and Panel containers ap• Describe how complex layouts with ne

work


As guage, how isJav ser interface(GU

Sun Services


Relevance

a platform-independent programming lana technology used to make the graphical uI) platform-independent?


t

Th

d in all Java

or extended;

is displayed onlass Component

bclass ofs:

Sun Services


Abstract Window Toolki

e AWT performs the following:

• Provides GUI components that are useapplets and applications

• Contains classes that can be composed classes can also be abstract

• Ensures that every GUI component thatthe screen is a subclass of the abstract cor MenuComponent

• Has Container, which is an abstract suComponent and includes two subclasse• Panel

• Window

Sun Services

The java.awtPackage

java.lang.Object

ButtonCanvasCheckboxChoiceContainerLabelListScrollbarTextComponent

BorderLayoutCardLayoutCheckboxGroupColorEventFontFlowLayoutFontMetricsGraphicsGridBagLayoutGridLayoutImageInsetsPointPolygonRectangleToolkitMenuComponentComponent

MenuBarMenuItem Menu -- PopupMenu

CheckboxMenuItem

TextAreaTextField

PanelWindowScrollPane

DialogFrame

Applet (java.applet package)

FileDialog

Exceptions – AWTException Errors – AWTError

java.awt.geom.Dimension2D

java.lang.Object

Dimension



od.indow and

the display.nts that must

iner, such as a

Sun Services


Containers

• Add components with the add() meth• The two main types of containers are W

Panel.• A Window is a free floating window on • A Panel is a container of GUI compone

exist in the context of some other contawindow or applet.


s

n a container is

omponents by

etSize(), orthem in the

Sun Services


Positioning Component

• The position and size of a component idetermined by a layout manager.

• You can control the size or position of cdisabling the layout manager.You must then use setLocation(), ssetBounds() on components to locatecontainer.


Fra

(true) to

out managerhe default

Sun Services


Frames

mes have the following characteristics:

• Are a subclass of Window• Have title and resizing corners• Are invisible initially; use setVisible

expose the frame• Have BorderLayout as the default lay• Use the setLayout method to change t

layout manager


s

12345678910111213141516171819

Sun Services


The FrameExampleClas

import java.awt.*;

public class FrameExample { private Frame f; public FrameExample() { f = new Frame("Hello Out There!"); }

public void launchFrame() { f.setSize(170,170); f.setBackground(Color.blue); f.setVisible(true); }

public static void main(String args[]) { FrameExample guiWindow = new FrameExample(); guiWindow.launchFrame(); }}


dows

Sun Services


Example Frame

Solaris OS Microsoft Win


.n layout

Sun Services


Panels

• Panels provide a space for components• This enables subpanels to have their ow

manager.


ss

12345678910

Sun Services


The FrameWithPanelCla

import java.awt.*;

public class FrameWithPanel { private Frame f;private Panel pan;

public FrameWithPanel(String title) { f = new Frame(title);

pan = new Panel();}


s

111213141516171819202122232425262728

Sun Services


The FrameWithPanelClas

public void launchFrame() { f.setSize(200,200); f.setBackground(Color.blue); f.setLayout(null); // Use default layout

pan.setSize(100,100); pan.setBackground(Color.yellow); f.add(pan); f.setVisible(true); }

public static void main(String args[]) { FrameWithPanel guiWindow = new FrameWithPanel("Frame with Panel"); guiWindow.launchFrame(); }}


indows

Sun Services


Example Panel

Solaris OSMicrosoft W


Sun Services


Layout Managers

• FlowLayout

• BorderLayout

• GridLayout

• CardLayout

• GridBagLayout


s

ut

Sun Services


Default Layout Manager

Component

Container

Window

Frame Dialog

BorderLayout

Panel

Applet

FlowLayo


ple

123456789101112

Sun Services


A Simple FlowLayoutExam

import java.awt.*;

public class LayoutExample { private Frame f; private Button b1; private Button b2;

public LayoutExample() { f = new Frame("GUI example"); b1 = new Button("Press Me"); b2 = new Button("Don’t press Me"); }


ple

131415161718192021222324252627

Sun Services


A Simple FlowLayoutExam

public void launchFrame() { f.setLayout(new FlowLayout()); f.add(b1); f.add(b2); f.pack(); f.setVisible(true); }

public static void main(String args[]) { LayoutExample guiWindow = new LayoutExample(); guiWindow.launchFrame(); }

} // end of LayoutExample class


dows

Sun Services


Example of FlowLayout

Solaris OS Microsoft Win


er

Th haracteristics:

class

Sun Services


The FlowLayoutManag

e FlowLayout manager has the following c

• Forms the default layout for the Panel• Adds components from left to right• Alignment default is centered• Uses components’ preferred sizes• Uses the constructor to tune behavior


Sun Services


The FlowLayoutResizing

Solaris OS

After user orprogram resizes


s

1234567891011121314

Sun Services


The FlowExampleClas

import java.awt.*;

public class FlowExample { private Frame f; private Button button1; private Button button2; private Button button3;

public FlowExample() { f = new Frame("Flow Layout"); button1 = new Button("Ok"); button2 = new Button("Open"); button3 = new Button("Close"); }


151617181920212223242526272829

Sun Services


The FlowExampleClass

public void launchFrame() { f.setLayout(new FlowLayout()); f.add(button1); f.add(button2); f.add(button3); f.setSize(100,100); f.setVisible(true); }

public static void main(String args[]) { FlowExample guiWindow = new FlowExample(); guiWindow.launchFrame(); }}


ger

ult layout for

ns.

just

t vertically

Sun Services


The BorderLayoutMana

• The BorderLayout manager is the defathe Frame class.

• Components are added to specific regio• The resizing behavior is as follows:

• North, South, and Center regions adhorizontally

• East, West, and Center regions adjus


ayout

Sun Services


Organization of the Border LComponents

North

South

Eas

t

Wes

t

Center


ss

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Sun Services


The BorderExampleCla

import java.awt.*;

public class BorderExample { private Frame f; private Button bn, bs, bw, be, bc;

public BorderExample() { f = new Frame("Border Layout"); bn = new Button("B1"); bs = new Button("B2"); bw = new Button("B3"); be = new Button("B4"); bc = new Button("B5"); }


s

15161718192021222324252627282930

Sun Services


The BorderExampleClas

public void launchFrame() { f.add(bn, BorderLayout.NORTH); f.add(bs, BorderLayout.SOUTH); f.add(bw, BorderLayout.WEST); f.add(be, BorderLayout.EAST); f.add(bc, BorderLayout.CENTER); f.setSize(200,200); f.setVisible(true); }

public static void main(String args[]) { BorderExample guiWindow2 = new BorderExample(); guiWindow2.launchFrame(); }}


t

Sun Services


Example of BorderLayou

Solaris OS



er

t, and from top

columns.

Sun Services


The GridLayoutManag

• Components are added from left to righto bottom.

• All regions are sized equally.• The constructor specifies the rows and


s

123456789101112131415

Sun Services


The GridExampleClas

import java.awt.*;

public class GridExample { private Frame f; private Button b1, b2, b3, b4, b5, b6;

public GridExample() { f = new Frame("Grid Example"); b1 = new Button("1"); b2 = new Button("2"); b3 = new Button("3"); b4 = new Button("4"); b5 = new Button("5"); b6 = new Button("6"); }


161718192021222324252627282930313233

Sun Services


The GridExampleClass

public void launchFrame() { f.setLayout (new GridLayout(3,2)); f.add(b1); f.add(b2); f.add(b3); f.add(b4); f.add(b5); f.add(b6);

f.pack(); f.setVisible(true); }

public static void main(String args[]) { GridExample grid = new GridExample(); grid.launchFrame(); }}


ows

Sun Services


Example of GridLayout

Solaris OS

Microsoft Wind




Class

123456789101112131415

Sun Services


The ComplexLayoutExample

import java.awt.*;

public class ComplexLayoutExample { private Frame f; private Panel p; private Button bw, bc; private Button bfile, bhelp;

public ComplexLayoutExample() { f = new Frame("GUI example 3"); bw = new Button("West"); bc = new Button("Work space region"); bfile = new Button("File"); bhelp = new Button("Help"); }


lass

1617181920 rder2122232425262728293031 mple();323334

Sun Services


The ComplexLayoutExampleC

public void launchFrame() { // Add bw and bc buttons in the frame border f.add(bw, BorderLayout.WEST); f.add(bc, BorderLayout.CENTER); // Create panel for the buttons in the north bo p = new Panel(); p.add(bfile); p.add(bhelp); f.add(p, BorderLayout.NORTH); // Pack the frame and make it visible f.pack(); f.setVisible(true); }

public static void main(String args[]) { ComplexLayoutExample gui = new ComplexLayoutExa gui.launchFrame(); }}


rs

aris OS

Sun Services


Combining Layout Manage

Sol



ugh AWT just for this

sorPaneland

the componentow overlapped.

ct.drawing

Sun Services


Drawing in AWT

• You can draw in any Component (althoprovides the Canvas and Panel classespurpose).

• Typically, you create a subclass ofCanvaoverride the paint method.

• The paintmethod is called every timeis shown (for example, if another windthe component and was then removed)

• Every component has a Graphics obje• The Graphics class implements many

methods.


raphics

Sun Services


Various Shapes Drawn by the GObject

Sun

Java™ Programmi

Services

ng Language

Module 11

GUI Event Handling


in a GUI, including how

ed the event

ce for a variety

ethods for a

anonymous

Sun Services


Objectives

• Define events and event handling• Write code to handle events that occur • Describe the concept of adapter classes

and when to use them• Determine the user action that originat

from the event object details• Identify the appropriate listener interfa

of event types• Create the appropriate event handler m

variety of event types• Understand the use of inner classes and

classes in event handling


ke it useful?mouse click or

Sun Services


Relevance

• What parts of a GUI are required to ma• How does a graphical program handle a

any other type of user interaction?


penedents an event

ser’s interaction

vent e) {

Sun Services


What Is an Event?

• Events – Objects that describe what hap• Event sources – The generator of an ev• Event handlers – A method that receive

object, deciphers it, and processes the uFrame

Panel

Button

The user clicks on the button

Some Event HandleractionPerformed(ActionE ...}

ActionEvent


ndlers.

ts when theyat component.

vent e) {

vent e) {

Sun Services


Delegation Model

• An event can be sent to many event ha

• Event handlers register with componenare interested in events generated by th

Frame

Panel

Button

The user clicks on the button

Another Event Handler

One Event Handler

actionPerformed(ActionE ...}

actionPerformed(ActionE ...}ActionEvent


GUI

lers for the type

n one type of

ork among

Sun Services


Delegation Model

• Client objects (handlers) register with acomponent that they want to observe.

• GUI components only trigger the handof event that has occurred.

• Most components can trigger more thaevent.

• The delegation model distributes the wmultiple classes.


123456789101112131415161718

Sun Services


A Listener Example

import java.awt.*;

public class TestButton { private Frame f; private Button b;

public TestButton() { f = new Frame("Test"); b = new Button("Press Me!"); b.setActionCommand("ButtonPressed"); }

public void launchFrame() {b.addActionListener(new ButtonHandler());

f.add(b,BorderLayout.CENTER); f.pack(); f.setVisible(true); }


192021222324

Co

123 tener {456789

Sun Services


A Listener Example

public static void main(String args[]) { TestButton guiApp = new TestButton(); guiApp.launchFrame(); }}

de for the event listener looks like this:

import java.awt.event.*;

public class ButtonHandler implements ActionLis public void actionPerformed(ActionEvent e) { System.out.println("Action occurred"); System.out.println("Button’s command is: " + e.getActionCommand()); }}


java.util.EventObject

KeyEvent

MouseEvent

Sun Services


Event Categoriesjava.awt.AWTEvent ActionEvent

AdjustmentEvent

ComponentEvent

TextEvent

ContainerEvent

FocusEvent

InputEvent

WindowEvent

java.awt.event

ItemEvent


faces

Ca

Ac ActionEvent)

Item (ItemEvent)

Mo seEvent)useEvent)seEvent)eEvent)seEvent)

Momo

seEvent)Event)

Ke ent)vent)t)

Sun Services


Method Categories and Inter

tegory Interface Name Methods

tion ActionListener actionPerformed(

ItemListener itemStateChanged

use MouseListener mousePressed(MoumouseReleased(MomouseEntered(MoumouseExited(MousmouseClicked(Mou

usetion

MouseMotionListener mouseDragged(MoumouseMoved(Mouse

y KeyListener keyPressed(KeyEvkeyReleased(KeyEkeyTyped(KeyEven


ces

Ca

Foc sEvent)vent)

Ad hanged)

Co omponentEvent)ComponentEvent)(ComponentEvent)omponentEvent)

Sun Services


Method Categories and Interfa


us FocusListener focusGained(FocufocusLost(FocusE

justment AdjustmentListener adjustmentValueC(AdjustmentEvent

mponent ComponentListener componentMoved(CcomponentHidden(componentResizedcomponentShown(C


ces

Ca

Wi ndowEvent)dowEvent)WindowEvent)d(WindowEvent)dowEvent)WindowEvent)d(WindowEvent)

Co ontainerEvent)(ContainerEvent)

Tex (TextEvent)

Sun Services


Method Categories and Interfa


ndow WindowListener windowClosing(WiwindowOpened(WinwindowIconified(windowDeiconifiewindowClosed(WinwindowActivated(windowDeactivate

ntainer ContainerListener componentAdded(CcomponentRemoved

t TextListener textValueChanged


12345 tener {6789101112

Sun Services


Complex Example

import java.awt.*;import java.awt.event.*;

public class TwoListenerimplements MouseMotionListener, MouseLis

private Frame f; private TextField tf;

public TwoListener() { f = new Frame("Two listeners example"); tf = new TextField(30); }


131415 se");16171819202122232425

Sun Services


Complex Example

public void launchFrame() { Label label = new Label("Click and drag the mou // Add components to the frame f.add(label, BorderLayout.NORTH); f.add(tf, BorderLayout.SOUTH); // Add this object as a listener f.addMouseMotionListener(this); f.addMouseListener(this); // Size the frame and make it visible f.setSize(300, 200); f.setVisible(true); }


2627282930313233343536373839404142

Sun Services


Complex Example

// These are MouseMotionListener events public void mouseDragged(MouseEvent e) { String s = "Mouse dragging: X = " + e.getX() + " Y = " + e.getY(); tf.setText(s); }

public void mouseEntered(MouseEvent e) { String s = "The mouse entered"; tf.setText(s); }

public void mouseExited(MouseEvent e) { String s = "The mouse has left the building"; tf.setText(s); }


434445 he46474849505152535455565758

Sun Services


Complex Example

// Unused MouseMotionListener method. // All methods of a listener must be present in t // class even if they are not used. public void mouseMoved(MouseEvent e) { }

// Unused MouseListener methods. public void mousePressed(MouseEvent e) { } public void mouseClicked(MouseEvent e) { } public void mouseReleased(MouseEvent e) { }

public static void main(String args[]) { TwoListener two = new TwoListener(); two.launchFrame(); }}


of a program to

re called when

Sun Services


Multiple Listeners

• Multiple listeners cause unrelated partsreact to the same event.

• The handlers of all registered listeners athe event occurs.


extend adapterthat you need.

1234 {5678910111213

Sun Services


Event Adapters

• The listener classes that you define canclasses and override only the methods

• An example is:import java.awt.*;import java.awt.event.*;

public class MouseClickHandler extends MouseAdapter

// We just need the mouseClick handler, so we use // an adapter to avoid having to write all the // event handler methods

public void mouseClicked(MouseEvent e) { // Do stuff with the mouse click... }}


lasses

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Sun Services


Event Handling Using Inner C

import java.awt.*;import java.awt.event.*;public class TestInner { private Frame f; private TextField tf; // used by inner class

public TestInner() { f = new Frame("Inner classes example"); tf = new TextField(30); }

class MyMouseMotionListener extends MouseMotionAd public void mouseDragged(MouseEvent e) { String s = "Mouse dragging: X = "+ e.getX( + " Y = " + e.getY();

tf.setText(s); } }


sses

192021 se");2223242526 ner());2728293031323334353637

Sun Services


Event Handling Using Inner Cla

public void launchFrame() { Label label = new Label("Click and drag the mou // Add components to the frame f.add(label, BorderLayout.NORTH); f.add(tf, BorderLayout.SOUTH); // Add a listener that uses an Inner class f.addMouseMotionListener(new MyMouseMotionListe f.addMouseListener(new MouseClickHandler()); // Size the frame and make it visible f.setSize(300, 200); f.setVisible(true); }

public static void main(String args[]) { TestInner obj = new TestInner(); obj.launchFrame(); }}


E s Classes

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Sun Services


vent Handling Using Anonymou

import java.awt.*;import java.awt.event.*;

public class TestAnonymous { private Frame f; private TextField tf;

public TestAnonymous() { f = new Frame("Anonymous classes example"); tf = new TextField(30); }

public static void main(String args[]) { TestAnonymous obj = new TestAnonymous(); obj.launchFrame(); }


E Classes

1819 se");2021222324 () {2526 )2728293031 Not shown3233343536

Sun Services


vent Handling Using Anonymous

public void launchFrame() { Label label = new Label("Click and drag the mou // Add components to the frame f.add(label, BorderLayout.NORTH); f.add(tf, BorderLayout.SOUTH); // Add a listener that uses an anonymous class f.addMouseMotionListener(new MouseMotionAdapter public void mouseDragged(MouseEvent e) { String s = "Mouse dragging: X = "+ e.getX( + " Y = " + e.getY(); tf.setText(s); } }); // <- note the closing parenthesis f.addMouseListener(new MouseClickHandler()); // // Size the frame and make it visible f.setSize(300, 200); f.setVisible(true); }}

Sun

Java™ Programmi

ns

Services

ng Language

Module 12

GUI-Based Applicatio


the events that

menu, and

d font of a

Sun Services


Objectives

• Identify the key AWT components andthey trigger

• Describe how to construct a menu bar, menu items in a Java GUI

• Understand how to change the color ancomponent


I for bothut. However,

ich GUIs can becomponents

UI frame?

Sun Services


Relevance

• You now know how to set up a Java GUgraphic output and interactive user inponly a few of the components from whbuilt have been described. What other would be useful in a GUI?

• How can you create a menu for your G


Co

But for receiving mouse

Can

Che to select an item

Che

Cho

Com nts, except menu

Con s

Dia and a border;al

Fra ws with window

Sun Services


AWT Components

mponent Type Description

ton A named rectangular box used clicks

vas A panel used for drawing

ckbox A component enabling the user

ckboxMenuItem A checkbox within a menu

ice A pull-down static list of items

ponent The parent of all AWT componecomponents

tainer The parent of all AWT container

log A top-level window with a titledialogs can be modeless or mod

me The base class of all GUI windomanager controls


Co

Lab

Lis namic set of items

Men , which contains a

Men

Pan st often to create

Scr r to select from a

Scr ts automatic for a single child

Sun Services


AWT Components


el A text string component

t A component that contains a dy

u An element under the menu barset of menu items

uItem An item within a menu

el A basic container class used mocomplex layouts

ollbar A component that enables a userange of values

ollPane A container class that implemenhorizontal and vertical scrollingcomponent


Co

Tex ser to enter a block

Tex ser to enter a single

Win s, without window

Sun Services


AWT Components


tArea A component that enables the uof text

tField A component that enables the uline of text

dow The base class of all GUI windowmanager controls


CoTy

u MM Text Win

But ✓

Can ✓

Che ✓

CheMen

Cho ✓

Com ✓

Con ✓

Dia ✓

Fra ✓

Lab ✓

Sun Services


AWT Listeners

mponentpe

Act Adj Cmp Cnt Foc Itm Key Mo

ton ✓ ✓ ✓ ✓ ✓

vas ✓ ✓ ✓ ✓

ckbox ✓ ✓ ✓ ✓ ✓

ckbox-uItem

✓

ice ✓ ✓ ✓ ✓ ✓

ponent ✓ ✓ ✓ ✓

tainer ✓ ✓ ✓ ✓ ✓

log ✓ ✓ ✓ ✓ ✓

me ✓ ✓ ✓ ✓ ✓

el ✓ ✓ ✓ ✓


CoTy

u MM Text Win

Lis ✓

Men

Pan ✓

Scr ✓

Scr ✓

Tex ✓ ✓

Tex ✓ ✓

Win ✓ ✓ ✓

Sun Services


AWT Listeners

mponentpe

Act Adj Cmp Cnt Foc Itm Key Mo

t ✓ ✓ ✓ ✓ ✓ ✓

uItem ✓

el ✓ ✓ ✓ ✓ ✓

ollbar ✓ ✓ ✓ ✓ ✓

ollPane ✓ ✓ ✓ ✓ ✓

tArea ✓ ✓ ✓ ✓

tField ✓ ✓ ✓ ✓ ✓

dow ✓ ✓ ✓ ✓ ✓


a menu

dd them to the

and add them

Sun Services


How to Create a Menu

1. Create a MenuBar object, and set it intocontainer, such as a Frame.

2. Create one or more Menu objects, and amenu bar object.

3. Create one or more MenuItem objects,to the menu object.


123

ndows

Sun Services


Creating a MenuBar

Frame f = new Frame("MenuBar");MenuBar mb = new MenuBar();f.setMenuBar(mb);

Solaris OS Microsoft Wi


123456789

Sun Services


Creating a Menu

Frame f = new Frame("Menu");MenuBar mb = new MenuBar();Menu m1 = new Menu("File");Menu m2 = new Menu("Edit");Menu m3 = new Menu("Help");mb.add(m1);mb.add(m2);mb.setHelpMenu(m3);f.setMenuBar(mb);


ndows

Sun Services


Creating a Menu

Solaris OSMicrosoft Wi


12345678910111213

Sun Services


Creating a MenuItem

MenuItem mi1 = new MenuItem("New");MenuItem mi2 = new MenuItem("Save");MenuItem mi3 = new MenuItem("Load");MenuItem mi4 = new MenuItem("Quit");mi1.addActionListener(this);mi2.addActionListener(this);mi3.addActionListener(this);mi4.addActionListener(this);m1.add(mi1);m1.add(mi2);m1.add(mi3);m1.addSeparator();m1.add(mi4);


ndows

Sun Services


Creating a MenuItem



tem

1234567891011121314 tent");1516

Sun Services


Creating a CheckBoxMenuI

MenuBar mb = new MenuBar();Menu m1 = new Menu("File");Menu m2 = new Menu("Edit");Menu m3 = new Menu("Help");mb.add(m1);mb.add(m2);mb.setHelpMenu(m3);f.setMenuBar(mb);.....MenuItem mi2 = new MenuItem("Save");mi2.addActionListener(this);m1.add(mi2);......CheckboxMenuItem mi5 = new CheckboxMenuItem("Persismi5.addItemListener(this);m1.add(mi5);


tem

ndows

Sun Services


Creating a CheckBoxMenuI



ts

Co I include:

Sun Services


Controlling Visual Aspec

mmands to control visual aspects of the GU

• Colors:setForeground()setBackground()

• Example:Color purple = new Color(255, 0, 255);Button b = new Button(“Purple”);b.setBackground(purple);


y

wing) toolkit.he components

much moree, JTree, and

Sun Services


J.F.C./Swing Technolog

• Java Foundation Class/Swing (J.F.C./Stechnology is a second-generation GUI

• It builds on top of AWT, but supplants twith lightweight versions.

• There are many more components, andcomplex components, including JTablJComboBox.

Sun

Java™ Programmi

Services

ng Language

Module 13

Threads


ology program,sed by that

rite platform-

when multiple

etween threads corruption

Sun Services


Objectives

• Define a thread• Create separate threads in a Java techn

controlling the code and data that are uthread

• Control the execution of a thread and windependent code with threads

• Describe the difficulties that might arisethreads share data

• Use waitand notify to communicate b• Use synchronized to protect data from


Ho le taskscon

Sun Services


Relevance

w do you get programs to perform multipcurrently?


Sun Services


Threads

• What are threads?Threads are a virtual CPU.

• The three parts of at thread are:• CPU• Code• Data

CPU

Code Data

A thread orexecution context


12345678910111213141516171819

Sun Services


Creating the Thread

public class ThreadTester { public static void main(String args[]) { HelloRunner r = new HelloRunner(); Thread t = new Thread(r); t.start(); }}class HelloRunner implements Runnable { int i; public void run() { i = 0; while (true) { System.out.println("Hello " + i++); if ( i == 50 ) { break; } } }}


characteristics:ble instance.e.

”nner

Sun Services


Creating the Thread

• Multithreaded programming has these• Multiple threads are from one Runna• Threads share the same data and cod

• For example:Thread t1 = new Thread(r);Thread t2 = new Thread(r);

CPU

Code DataHelloRunner Instance “r

Thread t}New Thread

Class of HelloRu


Sun Services


Starting the Thread

• Use the start method.• Place the thread in a runnable state.


N Dead

run() Completes

Sun Services


Thread Scheduling

Runnable

ew

RunningScheduler

Blocked

Unblocked Event Blocked

start()


ple

123456789101112131415

Sun Services


Thread Scheduling Exam

public class Runner implements Runnable { public void run() { while (true) { // do lots of interesting stuff

// ...// Give other threads a chance

try {Thread.sleep(10);

} catch (InterruptedException e) { // This thread’s sleep was interrupted // by another thread } } }}


1234567891011121314

Sun Services


Terminating a Thread

public class Runner implements Runnable { private boolean timeToQuit=false;

public void run() { while ( ! timeToQuit ) { // continue doing work } // clean up before run() ends }

public void stopRunning() { timeToQuit=true; }}


12345678910111213

Sun Services


Terminating a Thread

public class ThreadController { private Runner r = new Runner(); private Thread t = new Thread(r);

public void startThread() { t.start(); }

public void stopThread() { // use specific instance of Runner r.stopRunning(); }}


s

Sun Services


Basic Control of Thread

• Test threads:isAlive()

• Access thread priority:getPriority()setPriority()

• Put threads on hold:Thread.sleep() // static methodjoin()Thread.yield() // static method


12345 a while678910111213141516

Sun Services


The joinMethod

public static void main(String[] args) { Thread t = new Thread(new Runner()); t.start(); ... // Do stuff in parallel with the other thread for ... // Wait here for the other thread to finish try { t.join(); } catch (InterruptedException e) { // the other thread came back early } ... // Now continue in this thread ...}


ads

1234567891011121314151617

Sun Services


Other Ways to Create Thre

public class MyThread extends Thread { public void run() { while ( true ) { // do lots of interesting stuff try { Thread.sleep(100); } catch (InterruptedException e) { // sleep interrupted } } }

public static void main(String args[]) { Thread t = new MyThread(); t.start(); }}


reads

Sun Services


Selecting a Way to Create Th

• Implement Runnable:• Better object-oriented design• Single inheritance• Consistency

• Extend Thread:Simpler code


yword

123456789101112131415

Sun Services


Using the synchronizedKe

public class MyStack {

int idx = 0; char [] data = new char[6];

public void push(char c) { data[idx] = c; idx++; }

public char pop() { idx--; return data[idx]; }}


lock flag. with the lock

h(char c) {(this) { c;

onized(this)

Sun Services


The Object Lock Flag

• Every object has a flag that is a type of• The synchronized enables interaction

flag.

Object this

public void pussynchronized data[idx] =idx++;

}}

Thread before synchr

Code orBehavior

Data orState


h(char c) {(this) { c;

nized(this)

Sun Services



Object this

public void pussynchronized data[idx] =idx++;

}}

Thread after synchro

Code orBehavior

Data orState


op() {d (this) {

ta[idx];

ing tozed(this)

Sun Services



Object this

public char psynchronizeidx--;return da

}}

Another thread, try

Waiting for

lock flag missing

object lock

Code orBehavior

Data orState

execute synchroni


Th ts:

d of the

eturn, ored code block

Sun Services


Releasing the Lock Flag

e lock flag is released in the following even

• Released when the thread passes the ensynchronized code block

• Released automatically when a break, rexception is thrown by the synchroniz


t Together

nchronized.ed should be

Sun Services


Using synchronized– Putting I

• All access to delicate data should be sy• Delicate data protected by synchroniz

private.


t Together

Th ent:

publ sy }}

publ//

}

Sun Services


Using synchronized– Putting I

e following two code segments are equival

ic void push(char c) {nchronized(this) {// The push method code

ic synchronized void push(char c) { The push method code


T ronization

N Dead

run() Completes

Sun Services


hread State Diagram With Synch

Blocked inObject’s

Lock Pool

Runnable

ew

RunningScheduler

Blocked


Lock Acquired Synchronized

start()


A d

from the other.

s

Sun Services


Deadlock

eadlock has the following characteristics:

• It is two threads, each waiting for a lock• It is not detected or avoided.• Deadlock can be avoided by:

• Deciding on the order to obtain lock• Adhering to this order throughout• Releasing locks in reverse order


notify

two threads.

at your

stination and

pon arrival at

Sun Services


Thread Interaction – waitand

• Scenario:Consider yourself and a cab driver as

• The problem:How do you determine when you aredestination?

• The solution:• You notify the cab driver of your de

relax.• The driver drives and notifies you u

your destination.


Th

Sun Services


Thread Interaction

read interactions include:

• The wait and notify methods• The pools:

• Wait pool• Lock pool


Th nd notify

Blocked inObject’s

Wait Pool

New Dead

un() Completes

)

wait()[Must have lock]/Releases lock

st

Sun Services


read State Diagram With wait a

notify() orBlocked inObject’s

Lock Pool

Runnable RunningScheduler

Blocked


r

Lock Acquired Synchronized

interrupt(

art()


zation

notifications in

Sun Services


Monitor Model for Synchroni

• Leave shared data in a consistent state.• Ensure programs cannot deadlock.• Do not put threads expecting different

the same wait pool.


123456789101112

Sun Services


The ProducerClass

package mod13;

public class Producer implements Runnable { private SyncStack theStack; private int num; private static int counter = 1;

public Producer (SyncStack s) { theStack = s; num = counter++; }


13141516171819 c);202122232425262728

Sun Services


The ProducerClass

public void run() { char c;

for (int i = 0; i < 200; i++) { c = (char)(Math.random() * 26 +’A’); theStack.push(c); System.out.println(“Producer” + num + “: “ + try { Thread.sleep((int)(Math.random() * 300)); } catch (InterruptedException e) { // ignore it } } } // END run method

} // END Producer class


123456789101112

Sun Services


The ConsumerClass

package mod13;

public class Consumer implements Runnable { private SyncStack theStack; private int num; private static int counter = 1;

public Consumer (SyncStack s) { theStack = s; num = counter++; }


1314151617 c);181920212223242526

Sun Services


The ConsumerClass

public void run() { char c; for (int i = 0; i < 200; i++) { c = theStack.pop(); System.out.println(“Consumer” + num + “: “ +

try { Thread.sleep((int)(Math.random() * 300)); } catch (InterruptedException e) { // ignore it } } } // END run method


Th

publ

pr ter>(400);

pu

}

pu

}}

Sun Services


The SyncStackClass

is is a sketch of the SyncStack class:

ic class SyncStack {

ivate List<Character> buffer = new ArrayList<Charac

blic synchronized char pop() {// pop code here

blic synchronized void push(char c) {// push code here


91011121314151617181920

Sun Services


The popMethod

public synchronized char pop() { char c; while (buffer.size() == 0) { try { this.wait(); } catch (InterruptedException e) { // ignore it... } } c = buffer.remove(buffer.size()-1); return c; }


22232425

Sun Services


The pushMethod

public synchronized void push(char c) { this.notify(); buffer.add(c); }


12345678910111213141516171819

Sun Services


The SyncTestClass

package mod13;public class SyncTest { public static void main(String[] args) { SyncStack stack = new SyncStack(); Producer p1 = new Producer(stack); Thread prodT1 = new Thread (p1); prodT1.start(); Producer p2 = new Producer(stack); Thread prodT2 = new Thread (p2); prodT2.start();

Consumer c1 = new Consumer(stack); Thread consT1 = new Thread (c1); consT1.start(); Consumer c2 = new Consumer(stack); Thread consT2 = new Thread (c2); consT2.start(); }}


ProdConsProdConsProdProdProdConsConsProdProdConsConsProdConsProdConsCons

Sun Services


The SyncTestClass

ucer2: Fumer1: Fucer2: Kumer2: Kucer2: Tucer1: Nucer1: Vumer2: Vumer1: Nucer2: Vucer2: Uumer2: Uumer2: Vucer1: Fumer1: Fucer2: Mumer2: Mumer2: T

Sun

Java™ Programmi

s

Services

ng Language

Module 14

Advanced I/O Stream


io package, and use them

treams, and

Sun Services


Objectives

• Describe the main features of the java.• Construct node and processing streams

appropriately• Distinguish readers and writers from s

select appropriately between them


he Javate from sources

pported in I/O

s of character

Sun Services


Relevance

• What mechanisms are in place within tprogramming language to read and wri(or sinks) other than files?

• How are international character sets suoperations?

• What are the possible sources and sinkand byte streams?


data from a

a, also called an

a, also called an

.y, and pipes

Sun Services


I/O Fundamentals

• A stream can be thought of as a flow of source or to a sink.

• A source stream initiates the flow of datinput stream.

• A sink stream terminates the flow of datoutput stream.

• Sources and sinks are both node streams• Types of node streams are files, memor

between threads or processes.


ses

Str racter Streams

Sou der

Sin ter

Sun Services


Fundamental Stream Clas

eam Byte Streams Cha

rce streams InputStream Rea

k streams OutputStream Wri


streams:

andled by

d by input

byte stream.haracter

Sun Services


Data Within Streams

• Java technology supports two types of character and byte.

• Input and output of character data is hreaders and writers.

• Input and output of byte data is handlestreams and output streams:• Normally, the term stream refers to a• The terms reader and writer refer to c

streams.


ds

Sun Services


The InputStreamMetho

• The three basic read methods are:int read()int read(byte[] buffer)int read(byte[] buffer, int offset, int length)

• Other methods include:void close()int available()long skip(long n)boolean markSupported()void mark(int readlimit)void reset()


ds

h)

Sun Services


The OutputStreamMetho

• The three basic write methods are:void write(int c)void write(byte[] buffer)void write(byte[] buffer, int offset, int lengt

• Other methods include:void close()void flush()


Sun Services


The ReaderMethods

• The three basic read methods are:int read()int read(char[] cbuf)int read(char[] cbuf, int offset, int length)

• Other methods include:void close()boolean ready()long skip(long n)boolean markSupported()void mark(int readAheadLimit)void reset()


h)

Sun Services


The WriterMethods

• The basic write methods are:void write(int c)void write(char[] cbuf)void write(char[] cbuf, int offset, int length)void write(String string)void write(String string, int offset, int lengt

• Other methods include:void close()void flush()


Ty ms

Fil StreamtStream

Mearr

InputStreamOutputStream

Mestr

Pip tStreamutStream

Sun Services


Node Streams

pe Character Streams Byte Strea

e FileReaderFileWriter

FileInputFileOutpu

mory:ay

CharArrayReaderCharArrayWriter

ByteArrayByteArray

mory:ing

StringReaderStringWriter

N/A

e PipedReaderPipedWriter

PipedInpuPipedOutp


Th sing a manualbu

jav

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Sun Services


A Simple Example

is program performs a copy file operation uffer:

a TestNodeStreams file1 file2

import java.io.*;

public class TestNodeStreams { public static void main(String[] args) { try { FileReader input = new FileReader(args[0]); FileWriter output = new FileWriter(args[1]); char[] buffer = new char[128]; int charsRead;

// read the first buffer charsRead = input.read(buffer);


13141516171819202122232425262728

Sun Services


A Simple Example

while ( charsRead != -1 ) {// write the buffer out to the output fileoutput.write(buffer, 0, charsRead);

// read the next buffercharsRead = input.read(buffer);

}

input.close(); output.close(); } catch (IOException e) { e.printStackTrace(); } }}


Th sing a built-inbu

jav

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Sun Services


Buffered Streams

is program performs a copy file operation uffer:

a TestBufferedStreams file1 file2

import java.io.*;

public class TestBufferedStreams { public static void main(String[] args) { try { FileReader input = new FileReader(arg BufferedReader bufInput = new BufferedReader FileWriter output = new FileWriter(arg BufferedWriter bufOutput = new BufferedWriter String line;

// read the first line line = bufInput.readLine();


141516171819202122232425262728

Sun Services


Buffered Streams

while ( line != null ) {// write the line out to the output filebufOutput.write(line, 0, line.length());bufOutput.newLine();// read the next lineline = bufInput.readLine();

}bufInput.close();

bufOutput.close();} catch (IOException e) {

e.printStackTrace(); } }}


Program

Data Sink

Sun Services


I/O Stream Chaining

Data Source

FileInputStreamBufferedInputStream

DataInputStream

Program

FileOutputStreamBufferedOutputStream

DataOutputStream

Input Stream Chain

Output Stream Chain


Ty ams

Bu InputStreamOutputStream

Filt nputStreamutputStream

Cobetand

Perobjser

putStreamtputStream

Sun Services


Processing Streams

pe Character Streams Byte Stre

ffering BufferedReaderBufferedWriter

BufferedBuffered

ering FilterReaderFilterWriter

FilterIFilterO

nvertingween bytes character

InputStreamReaderOutputStreamWriter

formingectialization

ObjectInObjectOu


Ty ams

Percon

tStreamutStream

Co erInputStream

Pee InputStream

Pri eam

Sun Services


Processing Streams

pe Character Streams Byte Stre

forming dataversion

DataInpuDataOutp

unting LineNumberReader LineNumb

king ahead PushbackReader Pushback

nting PrintWriter PrintStr


rarchy

nputStream

ackInputStream

redInputStream

umberInputStream

Sun Services


The InputStreamClass Hie

InputStream

FileInputStream

ObjectInputStream

PipedInputStream

StringBufferInputStream

FilterInputStream

ByteArrayInputStream

DataI

Pushb

Buffe

LineN

SequenceInputStream


rarchy

aOutputStream

ntStreamntStream

feredOutputStream

Sun Services


The OutputStreamClass Hie

OutputStream

FileOutputStream

ObjectOutputStream

FilterOutputStream

ByteArrayOutputStream

Dat

PriPri

Buf

PipedOutputStream


hy

eader

erReader

ader

Sun Services


The ReaderClass Hierarc

Reader

BufferedReader

CharArrayReader

PipedReader

FilterReader

StringReader

FileRInputStreamReader

LineNumb

PushbackRe


hy

eWriter

Sun Services


The WriterClass Hierarc

Writer

BufferedWriter

CharArrayWriter

PrintWriter

PipedWriter

FilterWriter

StringWriter

FilOutputStreamWriter

Sun

Java™ Programmi

Services

ng Language

Module 15

Networking


nection

forservers

Sun Services


Objectives

• Develop code to set up the network con• Understand the TCP/IP Protocol• Use ServerSocket and Socket classes

implementation of TCP/IP clients and


Ho nt machine anda s

Sun Services


Relevance

w can a communication link between a clieerver on the network be established?


Th

So

am and an

ams.

Se

Set telephonesys ch must belist

Sun Services


Networking

is section describes networking concepts.

ckets

• Sockets hold two streams: an input streoutput stream.

• Each end of the socket has a pair of stre

tting Up the Connection

up of a network connection is similar to a tem: One end must dial the other end, whiening.


o.com

Sun Services


Networking

client.bar.com

client.baz.com

server.fo

18000

18002

3000


ology

following:hinese at the server

Sun Services


Networking With Java Techn

• To address the connection, include the • The address or name of remote mac• A port number to identify the purpo

• Port numbers range from 0–65535.


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Sun Services


Java Networking Mode

Server

ServerSocket (port #)

OutputStream

InputStream

Socket.close()

Client

Socket (host, por

OutputStream

InputStream

Socket.close(

Register withthis service

Wait for aconnection

(Attempt to connect)Socket()

ServerSocket.accept()


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Sun Services


Minimal TCP/IP Server

import java.net.*;import java.io.*;

public class SimpleServer { public static void main(String args[]) { ServerSocket s = null;

// Register your service on port 5432 try {

s = new ServerSocket(5432); } catch (IOException e) { e.printStackTrace(); }


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Sun Services



// Run the listen/accept loop forever while (true) { try { // Wait here and listen for a connection

Socket s1 = s.accept();

// Get output stream associated with the so OutputStream s1out = s1.getOutputStream( BufferedWriter bw = new BufferedWriter( new OutputStreamWriter(s1out));

// Send your string! bw.write(“Hello Net World!\n”);


2829 socket303132333435363738394041

Sun Services



// Close the connection, but not the serverbw.close();s1.close();

} catch (IOException e) { e.printStackTrace(); } // END of try-catch

} // END of while(true)

} // END of main method

} // END of SimpleServer program


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Sun Services


Minimal TCP/IP Client

import java.net.*;import java.io.*;

public class SimpleClient {

public static void main(String args[]) {

try { // Open your connection to a server, at port // localhost used here

Socket s1 = new Socket("127.0.0.1", 5432)

// Get an input stream from the socket InputStream is = s1.getInputStream(); // Decorate it with a "data" input stream DataInputStream dis = new DataInputStream(is)


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Sun Services


Minimal TCP/IP Client

// Read the input and print it to the screen System.out.println(dis.readUTF());

// When done, just close the steam and connec dis.close(); s1.close();

} catch (ConnectException connExc) { System.err.println("Could not connect.");

} catch (IOException e) { // ignore } // END of try-catch

} // END of main method

} // END of SimpleClient program

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