oracle10g java programming - electronic presentation.pdf

8/15/2019 Oracle10g Java Programming - Electronic Presentation.pdf

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Oracle10g: Java Programming

Electronic Presentation

D17249GC11

Edition 1.1

August 2004

D39817


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Copyright © 2004, Oracle. All r ights reserved.

This documentation contains proprietary information of Oracle Corporation. It is provided under a

license agreement containing restrictions on use and disclosure and is also protected by copyright

law. Reverse engineering of the software is prohibited. If this documentation is delivered to a U.S.

Government Agency of the Department of Defense, then it is delivered with Restricted Rights and the

following legend is applicable:

Restricted Rights Legend

Use, duplication or disclosure by the Government is subject to restrictions for commercial computer

software and shall be deemed to be Restricted Rights software under Federal law, as set forth in

subparagraph (c)(1)(ii) of DFARS 252.227-7013, Rights in Technical Data and Computer Software

(October 1988).

This material or any portion of it may not be copied in any form or by any means without the express

prior written permission of Oracle Corporation. Any other copying is a violation of copyright law and

may result in civil and/or criminal penalties.

If this documentation is delivered to a U.S. Government Agency not within the Department of

Defense, then it is delivered with “Restricted Rights,” as defined in FAR 52.227-14, Rights in Data-

General, including Alternate III (June 1987).

The information in this document is subject to change without notice. If you find any problems in the

documentation, please report them in writing to Education Products, Oracle Corporation, 500 Oracle

Parkway, Box SB-6, Redwood Shores, CA 94065. Oracle Corporation does not warrant that this

document is error-free.

All references to Oracle and Oracle products are trademarks or registered trademarks of Oracle

Corporation.

All other products or company names are used for identification purposes only, and may be

trademarks of their respective owners.

Authors

Jeff Gallus

Glenn Stokol

Technical Contributors

and Reviewers

Kenneth Cooper Peter Driver Christian DugasCraig Hollister Chika Izumi

Pete LaseauGlenn MaslenMonica MotleyGayathri Rajagopal

Publisher

Poornima G


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Copyright © 2004, Oracle. All rights reserved.

Introduction


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I-2 Copyright © 2004, Oracle. All rights reserved.

Objectives

After completing this course, you should be able to do

the following:• Write stand-alone applications with the Java

programming language

• Develop and deploy an application• Build, generate, and test application components

by using Oracle JDeveloper 10g


5/434I-3 Copyright © 2004, Oracle. All rights reserved.

Course Overview

• This course teaches you how to write Java

applications.• You also learn how to build, debug, and deploy

applications by using Oracle JDeveloper 10g.

• The development environment is OracleJDeveloper 10g and the Oracle Database.


6/434Copyright © 2004, Oracle. All rights reserved.

Introducing the Java

and Oracle Platforms


7/4341-2 Copyright © 2004, Oracle. All rights reserved.

Objectives

After completing this lesson, you should be able to do

the following:• Identify the key elements of Java

• Describe the Java Virtual Machine (JVM)

• Examine how Java is used to build applications• Identify the key components of the J2SE Java

Development Kit (known as JDK or SDK)

• Describe Java deployment options



What Is Java?

Java:

• Is a platform and an object-oriented language• Was originally designed by Sun Microsystems for

consumer electronics

• Contains a class library• Uses a virtual machine for program execution



Key Benefits of Java

• Object-oriented

• Interpreted and platform-independent• Dynamic and distributed

• Multithreaded

• Robust and secure



An Object-Oriented Approach

• Objects and classes

– An object is a run-time representation of a “ thing.” – A class is a “ static definition of things.”

• Class models elaborate:

– Existing classes and objects – Behavior, purpose, and structure

– Relationships between classes

– Relationships between run-time objects

• Same models exist throughout the project.

Analysis ImplementationIntegrationand testing

Design

CLASS MODELS



Platform Independence

• Java source code is stored as text in a .java file.

• The .java file is compiled into .class files.• A .class fi le contains Java bytecodes

(instructions).

• The bytecodes are interpreted at run time. – The Java .class fi le is the executable code.

Compile

Movie.java

JVM

Running program Movie.class

(javac) (java)



Using Java with Enterprise

Internet ComputingWeb

server

Application

server

Presentation Businesslogic

• Servlets

• JavaServer

Pages (JSPs)

• Enterprise

JavaBeans (EJB)

• CORBA

Client Data



Using the Java Virtual Machine

Operating system

JVM

Application



How Does JVM Work?

• The class loader loads all required classes.

– JVM uses a CLASSPATH setting to locate class files.• JVM Verifier checks for il legal bytecodes.

• JVM Verifier executes bytecodes.

– JVM may invoke a Just-In-Time (JIT) compiler.• Memory Manager releases memory used by the

dereferenced object back to the OS.

– JVM handles Garbage collection.


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1-10 Copyright © 2004, Oracle. All rights reserved.

Benefits of Just-In-Time (JIT) Compilers

JIT compilers:

• Improve performance• Are useful if the same bytecodes are executed

repeatedly

• Translate bytecodes to native instruction• Optimize repetitive code, such as loops

• Use Java HotSpot VM for better performance and

reliability


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Implementing Security

in the Java Environment

Interface-specific access

Class loader

Bytecode verifier

Language and compiler


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Deployment of Java Applications

• Client-side deployment:

– JVM runs stand-alone applications from thecommand line.

– Classes load from a local disk, eliminating the need

to load classes over a network.

• Server-side deployment:

– Serves multiple clients from a single source

– Is compatible with a multit ier model for Internet

computing.


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Using Java with Oracle 10g

Oracle

database

Web

server Client

Application

server

PresentationBusiness

logic

Data

Oracle

Application Server


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Java Software Development Kit

Sun Java J2SE (known as JDK and Java SDK)

provides:• Compiler (javac)

• Core class library

– classes.zip

– rt.jar

• Debugger (jdb)

• Bytecode interpreter: The JVM (java)

• Documentation generator (javadoc)

• Java Archive utility (jar)

• Others

J2SE


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Using the Appropriate Development Kit

Java2 comes in three sizes:

• J2ME (Micro Edition): Version specifically targetedat the consumer space

• J2SE (Standard Edit ion): Complete ground-up

development environment for the Internet

• J2EE (Enterprise Edition): Everything in the J2SE

plus an application server and prototyping tools


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Integrated Development Environment

Development

UML

ADF

XML

SCM

Synchronized changes

Debug

Exchange

Database

HTML

Deployment


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Exploring the JDeveloper Environment

System Navigator Code Editor Property Inspector

Component Palette


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Oracle10g Products


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Summary

In this lesson, you should have learned the following:

• Java code is compiled into platform-independentbytecodes.

• Bytecodes are interpreted by JVM.

• Java applications can be stand-alone orimplemented across an Internet-computing model.


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Defining Object-Oriented Principles


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Objectives


the following:• Define objects and explain how they are used

• Associate objects so that they can communicate

and interact via messages

• Define classes and explain how they are used

• Describe object-oriented (OO) principles: classes,

objects, and methods

• Describe the value of Reusable Software

Components

• Examine the OO model that is used in this course


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What Is Modeling?

• Models perform the following functions:

– Describe exactly what the business needs – Facil itate discussion

– Prevent mistakes

• Modeling and implementation are treated

separately.

• Before coding can begin, the model must be

correct.


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What Are Classes and Objects?

• A class:

– Models an abstraction of objects – Defines the attr ibutes and behaviors of

objects

– Is the blueprint that defines an object

• An object:

– Is stamped out of the class mold

– Is a single instance of a class

– Retains the structure and behavior of a class


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An Object’s Attributes Maintain Its State

• Objects have knowledge about their current state.

• Each piece of knowledge is called an attribute. – The values of attributes dictate the objects’ state.

Attribute: Ink amount

Attribute: Cash available

Object: My blue pen

Object: Acme Bank ATM


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Objects Have Behavior

• An object exists to provide behavior (functionality)

to the system.• Each distinct behavior is called an operation.

Operation: Write

Operation: Withdraw

Object: My blue pen

Object: Acme Bank ATM


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Objects Are Modeled as Abstractions

• A Java object is modeled as an abstract

representation of a real-world object.• Model only those attributes and operations that

are relevant to the context of the problem.

Real-world attr ibutes/operations that you may not want to model:

• Attributes: Ink color

• Operations: Refil l, change color, point, write

• Attributes: Model, manufacturer, price

• Operations: Change price

Context: Product catalogReal-world attributes/operations that you may want to model:


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A PC may be

an object.

A PC may have a

keyboard, mouse, and

network card, all of which

may be objects.

A PC may have a

CD drive, which

may be an object.

Defining Object Composition

• Objects can be composed of other objects.

• Objects can be part of other objects.• This relationship between objects is known as

aggregation.


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The Donut Diagram

getAge()

Client or sender

Person

Messagenameaddress

birthdate

getName

setBirthdate getAge

getAddress setAddress


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Guided Practice:

Spot the Operations and Attributes


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Collaborating Objects

Collaborating objects work together to complete a task

and form the basis of an application system.

• All methods are defined within a class and are not

defined globally as in traditional languages.

• All objects are created from classes and contain

all the attr ibutes and methods of that class.

• Objects must associate with each other to

collaborate on common tasks.

• Associated objects communicate by sendingmessages.


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Objects Interact Through Messages

• Objects communicate by sending messages.

• A sending object must be associated with orlinked to the receiving object.

• The message sender requests the receiver toperform the operation that is named in themessage.

• This communication is similar to calling aprocedure:

– The sender calls a method of the receiver.

– The receiver executes the called method.

• Calling a method is always in the context of aparticular object: – myPen.write( ): Object-oriented programming

– write (myPen): Traditional structured

programming


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When you create my blue pen, you do not have to

specify its operations or attributes. You simply

say what class it belongs to.

What Is a Class?

• A class is a template for objects.

• A class definition specifies the operations andattributes for all instances of that class.

• A class is used to manage complexity.


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C i Cl d Obj


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Comparing Classes and Objects

• Classes are static definitions that you can use to

understand all the objects of that class.

• Objects are the dynamic entit ies that exist in the

real world and your simulation of it.

• Caution: OO people almost always use the words

classes and objects interchangeably; you mustunderstand the context to differentiate between

the two meanings.

Wh t I E l ti ?


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What Is Encapsulation?

Encapsulation hides the internal structure and

operations of an object behind an interface.

• A bank ATM is an object that gives its users cash.

– The ATM hides (encapsulates) the actual operation

of withdrawal from the user.

– The interface (way to operate the ATM) is providedby the keyboard functions, screen, cash dispenser,

and so on.

– Bypassing the encapsulation is bank robbery.

• Bypassing encapsulation in object-oriented

programming is impossible.

Wh t I I h it ?


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What Is Inheritance?

• There may be a commonality between different

classes.

• Define the common properties in a superclass.

• The subclasses use inheritance to include those

properties.

Savings account Checking account Account

U i th “ I Ki d f” R l ti hi


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Using the “ Is-a-Kind-of” Relationship

• A subclass object

“ is-a-kind-of”

superclass

object.

• A subclass must

have all theattributes and

behaviors of the

superclass.

Savings account

Account Pen

Pencil

What Is Polymorphism?


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What Is Polymorphism?

Polymorphism refers to:

• Many forms of the same operation• The ability to request an operation with the same

meaning to different objects. However, each object

implements the operation in a unique way.

• The principles of inheritance and object

substitution.

Load passengers

Architecture Rules for Reuse


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Architecture Rules for Reuse

Write code that contains:

• Events that can interact with your Java application• Properties that can be exposed

• Methods that can be invoked

Write code that supports:• Introspection or reflection

• Customization

• Persistence


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Order Entry UML Diagram


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Order Entry UML Diagram

Summary


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Summary


• An object is an abstraction of a real-world object.• A class is a template or blueprint for objects.

• Classes form inheritance trees: Operations that

are defined in one class are inherited by all

subclasses.

• Polymorphism frees the caller from knowing the

class of the receiving object.

Practice 2: Overview


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This practice covers:

• Identifying business objects for the Order Entrysystem

• Identifying methods for the classes

• Identifying attributes for the classes

• Searching for inheritance in the classes

• Examining UML class model for course

application

Order Entry System


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Order Entry System

Partial UML Class ModelOrder

id: int

orderDate: Date

shipDate: Date

shipMode: StringorderTotal: double

addItem()

removeItem()

setOrderDate()

getOrderDate()setShipDate()

:

OrderItem

lineNo: int

quantity: int

price: double

getQuantity()

setQuantity()

setPrice()

getPrice()

getItemTotal()

:

Customer

name: String

address: String

phone: StringgetName()

setName()

setAddress()

getAddress()

:

Companycontact: String

discount: int

getContact()

setContact()

:

Individual

licNumber: String

setLicNumber()

getLicNumber()

:

Product

id: intname: String

description: String

retailPrice: double

getPrice()

:


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Basic Java Syntax and Coding

Conventions

Objectives


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Objectives

After completing this lesson, you should be able to dothe following:

• Identify the key components of the Java language• Identify the three top-level constructs in a Java

program• Identify and describe Java packages• Describe basic language syntax and identify Java

keywords• Identify the basic constructs of a Java program

• Compile and run a Java application• Examine the JavaBean architecture as an exampleof standard coding practices

• Use the CLASSPATH variable and understand its

importance during compile and run time

Examining Toolkit Components


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Examining Toolkit Components

The J2SE/J2EE from Sun provides:

• Compiler • Bytecode interpreter

• Documentation generator

J2SE

Exploring Packages in J2SE/J2EE


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Exploring Packages in J2SE/J2EE

The J2SE/J2EE from Sun provides standard packages

for:

• Language

• Windowing

• Input/output

• Network communication

J2SE

Documenting Using the J2SE


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g g

The J2SE/J2EE from Sun provides documentation

support for:

• Comments

– Implementation

– Documentation

• Documentation generator

J2SE

Contents of a Java Source


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• A Java source file can contain three top-level

constructs:

– Only one package keyword followed by the package

name, per f ile

– Zero or more import statements followed by fully

qualified class names or “ *” qualified by a packagename

– One or more class or interface definitions

followed by a name and block

• File name must have the same name as the publicclass or public interface.

Establishing Naming Conventions


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g g

Naming conventions include:

• Class names

– Customer, RentalItem , InventoryItem

• File names

– Customer.java, RentalItem.java

• Method names

– getCustomerName(), setRentalItemPrice()

• Package names

– oracle.xml.xsql, java.awt, java.io

More About Naming Conventions


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g

• Variables:

– customerName, customerCreditLimit

• Constants:

– MIN_WIDTH, MAX_NUMBER_OF_ITEMS

• Uppercase and lowercase characters

• Numerics and special characters

Defining a Class


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Class definitions typically include:

• Access modifier

• Class keyword

• Instance fields

• Constructors

• Instance methods

• Class fields

• Class methods

Rental Class: Example


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public class Rental {

//Class variablestatic int lateFee;

// Instance variables

int rentalId;

String rentalDate;

float rentalAmountDue;

…

// Instance methods

float getAmountDue (int rentId) {

…

}

…

}

Declaration

Instance

variable

Instance

method

Access modifier

Creating Code Blocks


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• Enclose all class declarations.

• Enclose all method declarations.

• Group other related code segments.

public class SayHello {

public static void main(String[] args) {

System.out.println("Hello world");

}

}

Defining Java Methods


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• Always define within a class.

• Specify:

– Access modifier

– Static keyword

– Arguments

– Return type

[access-modifiers] [static] "return-type"

"method-name" ([arguments]) {

"java code block“ … }

return

Examples of a Method


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public float getAmountDue (String cust){

// method variables

int numberOfDays;float due;

float lateFee = 1.50F;

String customerName;

// method body

numberOfDays = getOverDueDays();

due = numberOfDays * lateFee;

customerName = getCustomerName(cust);return due;

}

Declaration

Method

variables

Method

statements

Return

Declaring Variables


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• You can declare variables anywhere in a class

block, and outside any method.

• You must declare variables before they are used

inside a method.

• It is typical to declare variables at the beginning of

a class block.• The scope or visibility of variables is determined

in the code block.

• You must initialize method variables before usingthem.

• Class and instance variables are automatically

initialized.

Examples of Variables


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in the Context of a Method public float getAmountDue (String cust) {

float due = 0;

int numberOfDays = 0;float lateFee = 1.50F;

{int tempCount = 1; // new code block

due = numberOfDays * lateFee;

tempCount++;

…

} // end code block

return due;}

Method

variables

Temporary

variables

Rules for Creating Statements


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• Use a semicolon to terminate statements.

• Define multiple statements within braces.

• Use braces for control statements.

What Are JavaBeans?


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A JavaBean is a platform-neutral reusable software

component that:

• Can be manipulated visually in a builder tool

• Communicates with other JavaBeans via events

• Comprises visible components that must inherit

from other visible components

• Provides an architecture for constructing the

building blocks of an application

Managing Bean Properties


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• Properties are the bean class member variables.

(Variables can be primitive types or objects.)

• A property can be:

– Unbound, which is a simple property

– Bound, which triggers an event when the field is

altered – Constrained, in which changes are accepted or

vetoed by interested listener objects

Exposing Properties and Methods


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Getter

methods(public)

Setter

methods(public void)

privateT var;T[] arr;

T getVar()

T[] getArr()

boolean isVar()

setVar(T val)

setArr(T[] val)

setVar(boolean val)

JavaBean Standards at Design Time


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The benefits at design t ime include:

• A facilitated interaction between designer, tool,

and bean

• Instantiated and functioning beans in a visual tool

• Highly iterative development environment

• Building applications in small bits that plug in and

out

• Storage and recovery of instantiated

objects

Compiling and Running

a Java Application


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a Java Application

• To compile a .java file:

• To execute a .class file:

• Remember that case matters.

prompt> javac SayHello.java

… compiler output …

prompt> java SayHello

Hello world

prompt>

The CLASSPATH Variable


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• Is defined in the operating system

• Directs the JVM and Java applications where tofind .class files

• References built-in libraries or user-defined

libraries

• Enables interpreter to search paths, and loadsbuilt-in classes before user-defined classes

• Can be used with “ javac” and “ java” commands

CLASSPATH: Example


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C:\>set CLASSPATH=D:labs\les03\classes\oe

Setting CLASSPATH

Location of .class files in the oe package

Summary


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• J2SE provides basic Java tools.

• J2SE provides a rich set of predefined classes and

methods.

• Java programs are made up of classes, objects,

and methods.

• Adhering to programming standards makes code

easier to read and reuse.



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• Examining the Java environment

• Writing and running a simple Java application

• Examining the course solution application

• Inspecting classes, methods, and variables

• Creating class files and an application class with a main( ) method

• Compiling and running an application


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Exploring Primitive Data Typesand Operators

Objectives


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After completing this lesson, you should be able to dothe following:

• Distinguish between reserved words and othernames in Java

• Describe Java primitive data types and variables

• Declare and initialize primitive variables• Use operators to manipulate primitive variables

• Describe uses of literals and Java operators

• Identify valid operator categories and operatorprecedence

• Use String object literals and the concatenation

operator

Reserved Keywords


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abstract

final

native private

protected

public

staticsynchronized

transient

volatile

strictfp

break

case

catchcontinue

default

do

elsefinally

for

if

return

switch

throw

try

while

boolean

byte

chardouble

float

int

longshort

void

truefalse

null

class

extends

implementsinterface

throws

instanceof

newsuper

this

import package

Variable Types


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• Eight primitive data types:

– Six numeric types

– A character type

– A Boolean type (for truth values)

• User-defined types:

– Classes – Interfaces

– Arrays

abc

Primitive Data Types


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Append uppercase or lowercase “ L” or “ F” to the numberto specify a long or a float number.

Integer Floating

PointCharacter

TrueFalse

byteshort

intlong

floatdouble

char boolean

1, 2, 3, 4207

0xff

0

3.0F.3337F

4.022E23

0.0f

'a' '\141''\u0061'

'\n'

‘\u0000’

truefalse

false

What Are Variables?


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• A variable is a basic unit of storage.

• Variables must be explicitly declared.

• Each variable has a type, an identifier, and ascope.

• There are three types of variables: class, instance,and method.

int myAge;

boolean isAMovie;

float maxItemCost = 17.98F;

Type

Identifier Init ial value

Title: “ BlueMoon”

Declaring Variables


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• Basic form of variable declaration:

– type identifier [ = value];

• Variables can be initialized when declared.


int itemsRented = 1;

float itemCost;

int i, j, k;

double interestRate;

}

Local Variables


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• Local variables are defined only within a methodor code block.

• They must be initialized before their contents areread or referenced.

class Rental {

private int instVar; // instance variable

public void addItem() {

float itemCost = 3.50F; // local variable

int numOfDays = 3; // local variable

}

}

Defining Variable Names


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• Variable names must start with a letter of thealphabet, an underscore, or a $ symbol.

• Other characters may include digits.

• Use meaningful names for variables, such as

customerFirstName and ageNextBirthday.

a item_Cost

itemCost _itemCostitem$Cost itemCost2

item#Cost item-Cost

item*Cost abstract2itemCost

What Are Numeric Literals?


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0 1 42 -23795 (decimal)

02 077 0123 (octal)

0x0 0x2a 0X1FF (hex)

365L 077L 0x1000L (long)

1.0 4.2 .47

1.22e19 4.61E-9

6.2f 6.21F

Integer literals

Floating-pointliterals

Six types: byte, short, int, long, float, double

What Are Nonnumeric Literals?


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true false

'a' '\n' '\t' '\077' '\u006F'

"Hello, world\n"String li terals

Boolean literals

Character li terals

Guided Practice: Declaring Variables


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Find the mistakes in this code and fix them:

byte sizeof = 200;

short mom = 43;

short hello mom;

int big = sizeof * sizeof * sizeof;

long bigger = big + big + big // ouch

double old = 78.0;

double new = 0.1;

boolean consequence = true;

boolean max = big > bigger;

char maine = "New England state";

char ming = 'd';

1

2

3

4

5

6

7

8

9

10

11

What Are Operators?


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• Operators manipulate data and objects.

• Operators take one or more arguments and

produce a value.

• There are 44 different operators.

• Some operators change the value of the operand.

Categorizing Operators


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There are five types of operators:

• Assignment

• Arithmetic

• Integer bitwise

• Relational

• Boolean

Using the Assignment Operator


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The result of an assignment operation is a value andcan be used whenever an expression is permitted.

• The value on the right is assigned to the identif ieron the left:

• The expression on the right is always evaluated

before the assignment.• Assignments can be strung together:

int var1 = 0, var2 = 0;

var1 = 50; // var1 now equals 50

var2 = var1 + 10; // var2 now equals 60

var1 = var2 = var3 = 50;

Working with Arithmetic Operators


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• Perform basic arithmetic operations.

• Work on numeric variables and literals.

int a, b, c, d, e;

a = 2 + 2; // addition

b = a * 3; // multiplication

c = b - 2; // subtraction

d = b / 2; // division

e = b % 2; // returns the remainder of division

More on Arithmetic Operators


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Most operations result in int or long:

• byte, char, and short values are promoted to

int before the operation.• If either argument is of the long type, then the

other is also promoted to long, and the result is of

the long type.

byte b1 = 1, b2 = 2, b3;

b3 = b1 + b2; // ERROR: result is an int

// b3 is byte

Examining Conversions and Casts


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• Java automatically converts a value of onenumeric type to a larger type.

• Java does not automatically “ downcast.”

byteshort

char int long

byte longintshortchar

Incrementing and Decrementing Values


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• The ++ and -- operators increment and decrement

by 1, respectively:

• The ++ and -- operators can be used in two ways:

int var1 = 3;

var1++; // var1 now equals 4

int var1 = 3, var2 = 0;

var2 = ++var1; // Prefix: Increment var1 first,

// then assign to var2.

var2 = var1++; // Postfix: Assign to var2 first,

// then increment var1.

Relational and Equality Operators


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greater thangreater than or equal to

less thanless than or equal toequal tonot equal to

>

>=

< var1); // res now equals true

Using the Conditional Operator (?:)


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• Useful alternative to if…else:

• If boolean_expr is true, the result is expr1;otherwise, the result is expr2:

boolean_expr ? expr1 : expr2

int val1 = 120, val2 = 0;

int highest;

highest = (val1 > val2) ? val1 : val2;

System.out.println("Highest value is " + highest);


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Compound Assignment Operators


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An assignment operator can be combined with anyconventional binary operator:

double total=0, num = 1;

double percentage = .50;

…

total = total + num; // total is now 1

total += num; // total is now 2

total -= num; // total is now 1

total *= percentage; // total is now .5total /= 2; // total is now 0.25

num %= percentage; // num is now 0

Operator Precedence

Operators CommentsOrder Assoc.


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Operators

++ -- + - ~

! (type)

* / %

+ - +> >>>

< > =

instanceof

== !=&

^

|

&&

||

?:

= op =

Comments

Unary operators

Multiply, divide, remainder

Add, subtract, add stringShift (>>> is zero-fill shift)

Relational, type compare

EqualityBit/logical ANDBit/logical exclusive ORBit/logical inclusive ORLogical ANDLogical ORConditional operator

Assignment operators

Order

1

2

34

5

67

8

9

10

11

12

13

Assoc.

R

L

LLL

LLLLLLRR


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Concatenating Strings


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The + operator creates and concatenates strings:

String name = "Jane ";

String lastName = "Hathaway";

String fullName;

name = name + lastName; // name is now//"Jane Hathaway"

// OR

name += lastName; // same result

fullName = name;

Summary


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• Java has eight primitive data types.

• A variable must be declared before it can be used.

• Java provides a comprehensive set of operators.

• Explicit casting may be necessary if you use data

types smaller than int.• The + and += operators can be used to create and

concatenate str ings.



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• Declaring and initializing variables

• Using various operators to compute new values

• Displaying results on the console


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Controlling Program Flow

Objectives


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the following:

• Use decision-making constructs• Perform loop operations

• Write switch statements


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Using Flow Control in Java


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• Each simple statement terminates with a

semicolon (;).

• Group statements by using the braces { }.• Each block executes as a single statement within

the flow of control structure.

{

boolean finished = true;

System.out.println("i = " + i);

i++;

}

Using the if Statement


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if ( boolean_expr )

statement1;

[elsestatement2];

if (i % 2 == 0)

System.out.println("Even");

else

System.out.println("Odd");

…if (i % 2 == 0) {

System.out.print(i);

System.out.println(" is even");

}

Examples:

General:

Nesting if Statements

if (speed >= 25)if (speed > 65)


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( p )

System.out.println("Speed over 65");

else

System.out.println("Speed >= 25 but


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int x = 3, y = 5;

if (x >= 0)

if (y < x)

System.out.println("y is less than x");

else

System.out.println("x is negative");

int x = 7;

if (x = 0)

System.out.println("x is zero");

int x = 14, y = 24;

if ( x % 2 == 0 && y % 2 == 0 );

System.out.println("x and y are even");

1

2

3

Defining the switch Statement


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• The switch

statement is useful

when selecting anaction from several

alternative integer

values.

• Integer_expr mustbe byte, int, char,

or short.

switch ( integer_expr ) {

case constant_expr1:statement1;

break;

case constant_expr2:

statement2;

break ;

[default:

statement3 ;]}


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Looping in Java

Th th t f l i J


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• There are three types of loops in Java:

– while

– do…while – for

• All loops have four parts:

– Initialization – Iteration condit ion

– Body

– Termination


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Using the do…while Loop

d hil loops place the test at the end:


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do…while loops place the test at the end:

do

statement;

while ( termination );

int i = 0;

do {


i++;

} while (i < 10);

Example:

Using the for Loop

for loops are the most common loops:


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for loops are the most common loops:

How would this for loop look using a while loop?

for (i = 0; i < 10; i++)

System.out.println(i);

for ( initialization; termination; iteration )statement;

Example:

More About the for Loop

• Variables can be declared in the initialization part


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• Variables can be declared in the init ialization partof a for loop:

• Init ialization and iteration can consist of a list ofcomma-separated expressions:

for (int i = 0; i < 10; i++)


for (int i = 0, j = 10; i < j; i++, j-- ) {


System.out.println("j = " + j);

}

Guided Practice: Spot the Mistakes

int x = 10; 1


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int x 10;

while (x > 0);

System.out.println(x--);

System.out.println("We have lift off!");

int x = 10;

while (x > 0)

System.out.println("x is " + x);

x--;

int sum = 0;

for (; i < 10; sum += i++);

System.out.println("Sum is " + sum);

1

2

3

The break Statement

• Breaks out of a loop or switch statement


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• Breaks out of a loop or switch statement

• Transfers control to the first statement after the

loop body or switch statement• Can simplify code but must be used sparingly

…

while (age = 250000)

break;

age++;}

…

Summary

In this lesson you should have learned the following:


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• The primary means of decision-making is the if

statement, with the optional else.• Java also offers the switch statement.

• Java provides three loop statements: while,

do…while, and for.• Use break and continue sparingly.




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• Performing tests by using if…else statements

• Using loops to perform iterative operations• Using the break statement to exit a loop

• Using the &&, ||, and ! operators in Boolean

expressions


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Building Applications with

Oracle JDeveloper 10g

Objectives



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the following:

• Create new projects, workspaces, andapplications

• Build Java applications in JDeveloper

• Enhance user interface frame design• Debug an application by using JDeveloper

debugger

• Define classes by using JDeveloper

• Describe how JDeveloper can be used to build

enterprise applications

What Is Oracle JDeveloper 10g?

• Oracle JDeveloper 10g provides an integrated


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Oracle JDeveloper 10g provides an integrated

development environment (IDE).

• Build, compile, and run Java applications by usingOracle JDeveloper.

• Use wizards to help build source code.

• View objects from many perspectives: code,structure, layout, and so on.

Exploring the JDeveloper Environment


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System Navigator Code Editor Property Inspector

Component Palette

Examining Workspaces

• Contain multiple projects


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p p j

• Enable you to view

currently used objectsWorkspace

Navigator

pane

Structure

pane

What Are Projects?

• Contain related


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files

• Manage project andenvironment

settings

• Manage compiler

and debug options

Project

Project

files

Creating JDeveloper Items

• JDeveloper items are


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invoked by selecting

File > New.• They are categorized by

type:

– General

– Business Tier

– Client Tier

– Database Tier

– Web Tier

• Create any JDeveloper

element.

Creating an Application Workspace

In the General


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category, select

ApplicationWorkspace to invoke

the Property pane.

Specifying Project Details


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Adding a New J2SE


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New J2SE definitions include:

• Java executable

• A classpath• A source path

• A doc path

Looking at the Directory Structure

JDeveloper creates and stores .java and .class files

b i th f ll i ti


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by using the following convention:

• \jdev\mywork• Followed by the workspace

name

• Followed by the project name – \classes\\

– \src\\

• Followed by class and src files

Exploring the Skeleton Java Application

Contains application and frame classes


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Finding Methods and Fields

Find methods and fields by using the Structure pane.


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Customizing JDeveloper

Customize the IDE

L k d f l


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• Look and feel

• General environment• Dockable windows

• Component Palette

• Load preset keymapsRename classes and packages by using refactoring.

Using the Help System


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Obtaining Help on a Topic

Use [F1] to invoke

context-specific Help.


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Oracle JDeveloper 10g Debugger

• Helps find and fix program errors:

Run time errors


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– Run-time errors

– Logic errors• Allows control of execution

• Allows examination of variables

Setting Breakpoints

Setting breakpoints:

• Manage multiple breakpoints


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• Manage multiple breakpoints

• Manage conditional breakpoints• Define columns displayed in window

– Description

– Type – Status, and so on

• Control scope of action

– Global > Workspace > Project

Using the Debugger Windows

View Debug information:

• Classes: Displays list of loaded classes and status


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• Classes: Displays list of loaded classes and status

• Watch: Evaluates and displays expressions• Monitors: Displays information about active

monitors

• Threads: Displays the names and statuses of allthreads

• Smart Data: Analyzes source code near execution

point

• … and more


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Watching Data and Variables

• The Smart Data tab displays analyzed variables

and fields.


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• The Data tab displays arguments, local variables,and static f ields from the current context.

• To watch other variables:

– Select a variable in the source window and right-

click.

– Select Watch... at Cursor from the context menu.

– View the variable in the Watch tab.

– Right-click a data item to modify it.

Summary

In this lesson, you should have learned how:

• JDeveloper builds debugs and runs all types of


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JDeveloper builds, debugs, and runs all types of

Java applications• JDeveloper can be used to develop:

– Java applications

– Java servlets

– JSPs

– EJBs

• JDeveloper can be used to build enterprise

applications



• Exploring the Oracle JDeveloper 10g IDE


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Exploring the Oracle JDeveloper 10g IDE

• Creating a workspace and project• Including application files from the earlier lesson


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Objectives


the following:


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• Define instance variables and methods• Define the no-arg (default) constructor method

• Instantiate classes and call instance methods

• Perform encapsulation by using packages togroup related classes

• Control access with public and private access

modifiers

• Use class variables and methods

Using Java Classes

Methods Objects


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Packages

Objectreferences Attributes

Contained in a class


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Creating Objects

• Objects are typically created by using the new

operator:


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• For example, to create two Movie objects:

Movie mov1 = new Movie("Gone ...");

Movie mov2 = new Movie("Last ...");

ClassName objectRef = new ClassName();

title: “ Gone with…”rating: “ PG”

title: “ Last Action…”rating: “ PG-13”

Using the new Operator

The new operator performs the following actions:

• Allocates and initializes memory for the new


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object• Calls a special initialization method in the class,

called a constructor

• Returns a reference to the new object

Movie mov1 = new Movie("Gone with…");

mov1(When instantiated)

title: “ Gone with…”rating: “ PG”

Comparing Primitives and Objects

Primitive variables

hold a value.

Object variables

hold references.


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int i;

int j = 3; Movie mov1 = new Movie();

title: null

rating: nul l

mov1

Movie mov1;

mov1

0

3j

inull

Using the null Reference

• A special null value may be assigned to an object

reference, but not to a primitive.


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• You can compare object references to null.• You can remove the association to an object by

setting the object reference to null.

Movie mov1; //Declare object reference…

if ( mov1 == null) //Ref not initialized?

mov1 = new Movie(); //Create a Movie object

…

mov1 = null; //Forget the Movie object

Assigning References

Assigning one reference to another results in two

references to the same object:


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Movie mov1 = new Movie("Gone...");

mov1

Movie mov2 = mov1;

mov2

title: “ Gone with…”

rating: “ PG”


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Accessing public Instance Variables

public instance variables can be accessed by using

the dot operator:


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public class Movie {

public String title;

public String rating;

…

} Movie mov1 = new Movie(); mov1.title = "Gone ...";

…

if (mov1.title.equals("Gone ... ") )

mov1.rating = "PG";


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Calling a Method

Objects communicate by using messages:

• All methods are defined within a class and are not


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defined globally as in traditional languages.• When you call a method, it is always in the context

of a particular object.

– myPen.write( ): Object-oriented programming

– Write (myPen): Traditional structured

programming


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Returning a Value from a Method

• Use a return statement to exit a method and to

return a value from a method:


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• If the return type is void, then no return is needed.

• You can use a return without a value to terminate

a method with a void return type.

public class Movie { private String rating;

…

public String getRating () {

return rating

}

}

Calling Instance Methods


private String title, rating;


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public String getRating(){

return rating;

}

public void setRating(String newRating){

rating = newRating;

}

} Movie mov1 = new Movie();

String r = mov1.getRating();

if (r.equals("G")) …Use the dot

operator:

Applying Encapsulation in Java

• Instance variables must bedeclared as private.

var

aMethod


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• Only instance methods can access private instance variables.

• private decouples the interfaceof the class from its internal operation.

Movie mov1 = new Movie();

String rating = mov1.getRating();

String r = mov1.rating; // error: private. . .

if (rating.equals("G"))

aMethod()

Passing Primitives into Methods

When a primitive or object reference value is passed

into a method, a copy of the value is generated:


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public void aMethod(int arg) {

if (arg < 0 || arg > 100)

arg = 0;System.out.println("arg: " + arg);

}

int num = 150;

anObj.aMethod(num);

System.out.println("num: " + num);

arg

150

num

150


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What Are Class Variables?

Class variables:

• Belong to a class and are common to all instancesof that class


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• Are declared as static in class definitions


private static double minPrice; // class var

private String title, rating; // inst vars

Movie class variable Movie objects

title

rating

title

rating

titleratingminPrice

Initializing Class Variables

• Class variables can be initialized at declaration.

• Initialization takes place when the class is loaded.


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• Use a static initializer block for complexinitialization.

• All class variables are initialized implicitly to

default values depending on data type.


private static double minPrice = 1.29;

private String title, rating; private int length = 0;

What Are Class Methods?

Class methods are:

• Shared by all instances

• Useful for manipulating class variables


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p g

• Declared as static

A class method is called by using the name of theclass or an object reference.

public static void increaseMinPrice(double inc) {

minPrice += inc;

}

Movie.increaseMinPrice(.50);

mov1.increaseMinPrice(.50);

Guided Practice: Class Methods

or Instance Methods


private static float price = 3.50f;


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private String rating;…

public static void setPrice(float newPrice) {

price = newPrice;

} public String getRating() {

return String;

}

}

Movie.setPrice(3.98f); Movie

mov1 = new Movie(…);

mov1.setPrice(3.98f);String a = Movie.getRating();

String b = mov1.getRating();Legal or not?

Examples in Java

Examples of static methods and variables:

• main()


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• Math.sqrt()• System.out.println()

public class MyClass {


double num, root;

…

root = Math.sqrt(num);System.out.println("Root is " + root);

} …

Creating Classes Using the Class Editor


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What Are Java Packages?

oe


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Customer Order Util

OrderEntry OrderItem

Grouping Classes in a Package

• Include the package keyword followed by thepackage name at the top of the Java source file.Use the dot notation to show the package path.

If it th k k d th th


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• If you omit the package keyword, then thecompiler places the class in a default “ unnamed”package.

• Use the –d flag with the javac compiler to create

the package tree structure relative to the specifieddirectory.

• Running a main() method in a packaged classrequires:

– That the CLASSPATH contains the directory havingthe root name of the package tree

– That the class name must be qualif ied by itspackage name

Setting the CLASSPATH with Packages

The CLASSPATH includes the directory containing the

top level of the package tree:

Package name .class location


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C:\>set CLASSPATH=E:\Curriculum\courses\java\les06

CLASSPATH

Access Modifiers

acmevideo acmetools


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private

protected

public public

Summary


• A class definition specifies a template for building

objects with identical features, such as instance

i bl d th d


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variables and methods.

• An object is an instance of a particular class.

– Create an object by using new.

– Manipulate an object by using its public instancemethods.



• Defining new classes

• Specifying the classes’ instance variables and


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• Specifying the classes instance variables andinstance methods

• Creating Customer objects in main()

• Manipulating Customer objects by using public

instance methods


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Objectives


the following:

• Provide two or more methods with the same name

in a class


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in a class

• Provide one or more constructors for a class

• Use initializers to initialize both instance and class

variables

• Describe the class loading and initializing

process, and the object life cycle

• Define and use inner classes

Overloading Methods

• Several methods in a class can have the same

name.

• The methods must have different signatures.


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public void setPrice() {

price = 3.50F;}

public void setPrice(float newPrice) {

price = newPrice;

} …

}


mov1.setPrice();

mov1.setPrice(3.25F);

Using the this Reference

Instance methods receive an argument called this,

which refers to the current object.



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public void setRating(String newRating) {

this.rating = newRating;

}

void anyMethod() {



mov1.setRating("PG"); …

title: null

rating: nul l mov2

mov1

title : null

rating: “ PG”

this

Initializing Instance Variables

• Instance variables can be explicitly initialized at

declaration.

• Initialization happens at object creation.


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• All instance variables are initialized implicitly to

default values depending on data type.

• More complex initialization must be placed in a

constructor.


private String title;

private String rating = "G";

private int numOfOscars = 0;

What Are Constructors?

• For proper initialization, a class must provide a

constructor.

• A constructor is called automatically when an

object is created:


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object is created:

– It is usually declared public.

– It has the same name as the class.

– It must not specify a return type.

• The compiler supplies a no-arg constructor i f and

only if a constructor is not explicitly provided.

– If any constructor is explicitly provided, then thecompiler does not generate the no-arg constructor.

Defining and Overloading Constructors



private String rating = "PG";


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public Movie() {

title = "Last Action …";

}

public Movie(String newTitle) {

title = newTitle;

}

}


Movie mov2 = new Movie("Gone…

");

Movie mov3 = new Movie("The Good …");

The Movie class

now provides twoconstructors.

Sharing Code Between Constructors



private String rating;

A constructorcan call another

constructor byusing thi ()



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public Movie() {

this("G");

}

public Movie(String newRating) {

rating = newRating;

}}

yusing this().

What happenshere?


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Reclaiming Memory

• When all references to an object are lost, the

object is marked for garbage collection.

• Garbage collection reclaims memory that is used

by the object.


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y j

• Garbage collection is automatic.

• There is no need for the programmer to do

anything, but the programmer can give a hint toSystem.gc();.

Using the finalize() Method

• If an object holds a resource such as a fi le, then

the object should be able to clean it up.

• You can provide a finalize() method in that

class.


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• The finalize() method is called just before

garbage collection.


…

public void finalize() {

System.out.println("Goodbye");}

}

Any problems?

What Are Inner Classes?

• Inner classes are nested classes, defined in a

class or method.

• They enforce a relationship between two classes.

• They are of four types:


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They are of four types:

– Static

– Member

– Local

– Anonymous

public class Outer { …

class Inner { …

}

}

Enclosing class

Using Member Inner Class

• It is declared within another class.

• Nesting is allowed.

• It can access variables within its own class and

any enclosing classes.


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a y e c os g c asses

• It can only declare final static methods.

public class CalendarPopup {

...class MonthSelector {

class DayOfMonth{...};DayOfMonth[] NumberOfDaysInMonth...

}}


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Defining Anonymous Inner Classes

• They are defined at method level.

• They are declared within a code block.

• They lack the class, extends, and implements

keywords.


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y

• They cannot have a constructor.

public class Outer {

... public void outerMethod(){

... myObject.myAnonymous(new SomeOtherClass(){...

} )}

}

Using the Calendar Class

• It converts between a date object and a set of

integer fields.

• It represents a specific moment in time.

• Subclasses interpret a date according to the


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p g

specific calendar system.

public class Order {

... public void String getShipDate(){

...Calendar c = Calendar.getInstance();c.setTime(orderDate);

...}}

Summary


• Methods can be overloaded in Java.

• Instance methods receive a this reference to the

current object.


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• Most classes provide one or more constructors to

initialize new objects.

• Class variables and class methods can

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