Chapter1 Introduction to Java Overview of the Java What Is the Java Technology The Java Virtual Machine A First Application in Java A First Applet in Java

Chapter1 Introduction to Java

Overview of the Java What Is the Java Technology The Java Virtual Machine A First Application in Java A First Applet in Java A Basic Java Application Using OO Java Terminology and Technology Products

CCE JMU China ZhangJM 2008-09

Reference

Thinking in Java （中、英版） The Java Tutorial Sun Microsystems Java™ Programming Language （中、英版） ( 作者： Ken Arnold 、 James Gosling 、 David

Holmes)

Java 程序设计教程袁兆山等译机械工业出版社


Overview of Java

Past Today Future


• Originally named Oak• Main team members: Bill Joy, Patrick Naughton, Mike Sheridan, James Gosling• Original goal: use with home appliances• In 1994, team realized Oak was perfect for Internet• Announced in May of 1995• First non-beta release in 1996• Java technology is free

The Origin of the Java Programming Language





Java 的渗透力


Java belongs to the world


Joining & Sharing



What Is the Java Technology?

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

It is used for developing both Applets and Applications


Java Is A Programming Language


Java Is A Platform


Building a Better Language

• Object-oriented

• Distributed

• Multi-threading

• Security

• APIs (pre-written code)

• Easily portable to multiple platforms

(Write Once, Run Anywhere™)


Primary Goals of the Java Technology

• Provides an easy-to-use language by:

Avoiding many pitfalls of other languages

Being object-oriented

Enabling users to create streamlined and clear code

• Provides an interpreted environment for:

Improved speed of development

Code portability


Primary Goals of the Java Technology

The following features fulfill these goals:

• The JVM

• Garbage collection

• Code security


Java Programs

Applets and Applications

• Application – Runs in the operating system

• Applet – Runs in a browser, does smaller tasks


Basic Components

of a Computer



Applicationsmust use

same languages as

operating and

hardware


Two Ways of Solving the Communication Problem

Compiled

- communicates with only one kind of computer

Interpreted

- communicates with any kind of computer







How Applications Run

HowApplets

Run



A First Application in Java //A First Application in Java public class HelloWorld{ public static void main(String[] args){ System.out.println("Hello

World!"); } }


Run the Application HelloWorld


A first Applet in Java // A first Applet in Java import javax.swing.JApplet; // 导入 Java API 的 JApplet 类 import java.awt.Graphics; // 导入 Java API 的 JGraphics 类 public class HelloWorldApplet extends JApplet { public void paint( Graphics g ) { g.drawString( "Hello World!", 25, 25 ); } }创建 HTML 文件，以将 HelloWorldApplet.java 编译所得

HelloWorldApplet.class 载入浏览器运行。 HelloWorldApplet.html 文件为：

<html> <applet code="HelloWorldApplet.class" width=300 height=30> </applet> </html>


Run the applet HelloWorldApplet


Run the applet HelloWorldApplet







The Java

TechnologyProducts

and Terminology



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Chapter1 Introduction to Java Overview of the Java What Is the Java Technology The Java Virtual Machine A First Application in Java A First Applet in Java