computer programming (tmk 3102) lecture notes 2

8/9/2019 COMPUTER PROGRAMMING (TMK 3102) LECTURE NOTES 2

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Chapt er 2: In t roduc t ion t o JAVA

Session Plan (Week 2):To understand:Java Framework

Java runtime environmentTerm API, IDE and JDK


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TMK 3102-Chap 1: Introduction toJAVA

2

Hist ory of J AVA James Gosling and Sun Microsystems

Early name for Java - Oak

Java, May 20, 1995, Sun World

HotJava

The first Java-enabled Web browser

Early History Website:

http://java.sun.com/features/1998/05/birthday.html
http://java.sun.com/features/1998/05/birthday.htmlhttp://java.sun.com/features/1998/05/birthday.html


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3

Why J ava?The answer is that Java enables users to deploy applications

on the Internet for servers, desktop computers, and small

hand-held devices. The future of computing will be

profoundly influenced by the Internet, and Java promisesto remain a big part of that future.

Java is a general purpose programming language.

Java is the Internet programming language.


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4

J ava, Web, and Beyond Java can be used to develop Web

applications.

Java Applets Java Servlets and JavaServer Pages

(JSP)

Java can also be used to developapplications for hand-held devicessuch as Palm and cell phones


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5

Charac t er is t i c s o f Java

Java Is Simple

Java Is Object-Oriented

Java Is Distributed

Java Is Interpreted Java Is Robust

Java Is Secure

Java Is Architecture-Neutral

Java Is Portable

Java's Performance

Java Is Multithreaded

Java Is Dynamic

Java is partially modeledon C++, but greatlysimplified and improved.

Some people refer to Javaas "C++--" because it islike C++ but with morefunctionality and fewer

negative aspects.


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Java Is Simple


Java Is Distributed


Java Is Secure


Java Is Portable

Java's Performance


Java Is Dynamic

Java is inherently object-oriented.Although many object-oriented languagesbegan strictly as procedural languages,Java was designed from the start to beobject-oriented. Object-oriented

programming (OOP) is a popularprogramming approach that is replacingtraditional procedural programmingtechniques.

One of the central issues in software

development is how to reuse code.Object-oriented programming providesgreat flexibility, modularity, clarity, andreusability through encapsulation,inheritance, and polymorphism.


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Java Is Simple


Java Is Distributed


Java Is Secure


Java Is Portable

Java's Performance


Java Is Dynamic

Distributed computing involvesseveral computers working togetheron a network. Java is designed tomake distributed computing easy.Since networking capability isinherently integrated into Java,writing network programs is likesending and receiving data to andfrom a file.


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Java Is Simple


Java Is Distributed


Java Is Secure


Java Is Portable

Java's Performance


Java Is Dynamic

You need an interpreter to run Javaprograms. The programs arecompiled into the Java VirtualMachine code called bytecode. Thebytecode is machine-independentand can run on any machine thathas a Java interpreter, which is partof the Java Virtual Machine (JVM).


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Java Is Simple


Java Is Distributed


Java Is Secure


Java Is Portable

Java's Performance


Java Is Dynamic

Java compilers can detect manyproblems that would first show up atexecution time in other languages.

Java has eliminated certain types oferror-prone programming constructsfound in other languages.

Java has a runtime exception-

handling feature to provideprogramming support forrobustness.


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Java Is Simple


Java Is Distributed


Java Is Secure


Java Is Portable

Java's Performance


Java Is Dynamic

Java implements several securitymechanisms to protect your systemagainst harm caused by strayprograms.


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Java Is Simple


Java Is Distributed


Java Is Secure


Java Is Portable

Java's Performance


Java Is Dynamic

Write once, run anywhere

With a Java Virtual Machine (JVM),you can write one program that will

run on any platform.


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Java Is Simple


Java Is Distributed


Java Is Secure


Java Is Portable

Java's Performance


Java Is Dynamic

Because Java is architectureneutral, Java programs areportable. They can be run on anyplatform without being recompiled.


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Java Is Simple


Java Is Distributed


Java Is Secure


Java Is Portable

Java's Performance


Java Is Dynamic

Java can execute very fast with thesupport of multithreading, clusteringand load balancing.


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Java Is Simple


Java Is Distributed


Java Is Secure


Java Is Portable

Java's Performance


Java Is Dynamic

Multithread programming issmoothly integrated in Java,whereas in other languages youhave to call procedures specific to

the operating system to enablemultithreading.


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Java Is Simple


Java Is Distributed


Java Is Secure


Java Is Portable

Java's Performance


Java Is Dynamic

Java was designed to adapt to anevolving environment. New codecan be loaded on the fly withoutrecompilation. There is no need for

developers to create, and for usersto install, major new softwareversions. New features can beincorporated transparently asneeded.


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J DK

Java Development Kit (JDK)

JDK for

Standard Edition (SE) Enterprise Edition (EE) Mobile Edition (ME)

Use for producing JAVA program

Can be downloaded fromhttp://www.java.sun.com
http://www.java.sun.com/http://www.java.sun.com/


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J DK Edi t ions

Java Standard Edition (J2SE or Java SE) J2SE/Java SE can be used to develop client-side

standalone applications or applets.

Java Enterprise Edition (J2EE or Java EE) J2EE/Java EE can be used to develop server-side

applications such as Java servlets and JavaServerPages.

Java Micro Edition (J2ME or Java ME). J2ME/Java ME can be used to develop applications

for mobile devices such as cell phones.


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Quest ions

Why are we using JAVA?

List the characteristics of JAVA

Programming Language What is JVM? What it is for?

What is JDK? What is for?

Give example of JDKs.


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Firs t J ava Program

//This program prints Welcome to Java!

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

System.out.println("Welcome to Java!");

}

}

Example 1.1


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Creat e & Edi t J ava Sourc e Code

To use Notepad, type

notepad Welcome.java from the DOS prompt.


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Creat e & Edi t J ava Sourc e Code

To use WordPad, type

write Welcome.java

from the DOS prompt.


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Creat ing, Com pi l ing, and Running Program s

Source Code

Create/Modify Source Code

Compile Source Code

i.e., javac Welcome.java

Bytecode

Run Byteode

i.e., java Welcome

Result

If compilation errors

If runtime errors or incorrect result

package chapter1;

public class Welcome {

public static void main(String[] args) {System.out.println("Welcome to Java!");}

}

Method Welcome()

0 aload_0

Method void main(java.lang.String[])

0 getstatic #2 3 ldc #3

5 invokevirtual #4

Saved on the disk

stored on the disk

Source code (developed by the programmer)

Byte code (generated by the compiler for JVM

to read and interpret, not for you to understand)


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Com pi l ing and Running J ava

f rom t he Com m and Window

Set path to JDK bin directory

set path=c:\Program Files\java\jdk1.5.0\bin Set classpath to include the current directory

set classpath=. Compilejavac Welcome.java

Runjava Welcome


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Anat om y of a J ava Program

Comments Package Reserved words Modifiers Statements Blocks

Classes Methods The main method


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Comments

In Java, comments are preceded by (1) two slashes (//) in a line(2) enclosed between /* and */ in one or multiple lines. Whenthe compiler sees //, it ignores all text after // in the sameline. When it sees /*, it scans for the next */ and ignores anytext between /* and */.


package chapter1;


public static void main(String[] args) {


}

}


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Package

The second line in the program (package chapter1;)specifies a package name, chapter1, for the classWelcome. Forte compiles the source code inWelcome.java, generates Welcome.class, and stores

Welcome.class in the chapter1 folder.//This program prints Welcome to Java!

package chapter1;




}

}


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Reserved Words

Reserved words or keywords are words that have a specificmeaning to the compiler and cannot be used for otherpurposes in the program. For example, when the compilersees the word class, it understands that the word after classis the name for the class. Other reserved words in exampleprogram are public, static, and void.


package chapter1;


public static void main(String[] args) {System.out.println("Welcome to Java!");

}

}


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J ava K eyw ords

do new abstract break synchronized

if default assert private implements

int goto this throw protected

try return import public instanceof

byte else throws double transient

case void boolean short package

for final interface static extends

char long finally strictfp volatile

class float native super while

const catch continue switch


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Modi f iers

Java uses certain reserved words calledmodifiers that specify the properties of thedata, methods, and classes and how they

can be used. Examples of modifiers arepublic and static. Other modifiers areprivate, final, abstract, and protected. Apublic datum, method, or class can beaccessed by other programs. A private

datum or method cannot be accessed byother programs.


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Sta tements

A statement represents an action or asequence of actions. The statementSystem.out.println("Welcome to

Java!") in the example program is astatement to display the greeting"Welcome to Java!

Every statement in Java ends with asemicolon (;).


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Blocks

A pair of braces in a program forms a block thatgroups components of a program

public class Test {



}

}

Class blockMethod block


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Classes

The class is the essential Java construct. Aclass is a template or blueprint for objects.

To program in Java, you must understandclasses and be able to write and use them.The mystery of the class will continue to beunveiled throughout subject. For now,

though, understand that a program isdefined by using one or more classes.


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Methods

What is System.out.println? It is a method: acollection of statements that performs a sequence ofoperations to display a message on the console. Itcan be used even without fully understanding thedetails of how it works. It is used by invoking astatement with a string argument. The stringargument is enclosed within parentheses. In thiscase, the argument is "Welcome to Java!" You can

call the same println method with a differentargument to print a different message.


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m ain Method

The main method provides the control of program flow.The Java interpreter executes the application byinvoking the main method.

The main method looks like this:


// Statements;}


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J ava Program St ruc t ure

import and package section;

Class Sectionpublic class classIdentifier {

}

Global Declaration

Main method sectionpublic static void main (String[] args) {

}

Local Declaration

Java Statement


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Quest ions

List the anatomy of JAVA program.

Give example of JAVA keywords.

What is the meaning of modifiers? Give example of modifiers.


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TMK 3102 Chap 1: Introduction to 37

Thank you.

computer programming (tmk 3102) lecture notes 2

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