introduction to java kiyeol ryu java programming language

Introduction to Java

Kiyeol Ryu

Java Programming Language


2

The Overview of Java

Table of Contents

• Brief History • What is Java• Java Applets and Applications• Java Programming Environment


3


Brief History

• 1991 Green Project (Sun Micro Systems)

– Comsumer Electronics • 1991 Oak language (Jav

a)• 1992 *7 - First Product• 1993 CableTV Box - fail • 1994 WWW 에 적용• 1994 HotJava Browser• 1995 Sun World 95 • 1996 JDK 1.0.2• 1997 JDK 1.1• 1998 JDK 1.2

– (J2SE SDK 1.2)

• 2000 J2SE SDK 1.3• 2002 J2SE SDK 1.4

• 1989 WWW (CERN) concept

• 1993 Mosaic (NCSA)• 1993 Netscape

M. Adressen, J. Clark

• 1995 Netscape Licensed Java

• 1996 MicroSoft Licensed Java

• 1998 Motorola Licensed Java


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What is Java

• simple• object-oriented• distributed• interpreted• robust• secure• architecture neutral• portable• high-performance• multithreaded• dynamic

Ref: J. Gosling, et. al., The Java Language, A White Paper, Sun Microsystems,

1994


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Java is Simple

• The syntax of Java is a cleaned-up version of the syntax for C++.

– header files– pointer– unions– operator overloading– virtual base classes– typedef– stuct– explicit memory management– etc.

C++C

Java


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Java is Object-Oriented

• Models real world entities as objects• Abstracts out data as classes • Reuses classes through inheritance


7


Java is Distributed

• Extensive TCP/IP networking capabilities• Interactivities with protocols to retrieve

information such as HTTP, FTP• Ease of accessing remote files


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Java is Interpreted

• The java interpreter can directly execute instructions in its object code.

• Java bytecode• Architecture-neutral


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Java is Robust

• No pointer• Array bounds checking• Exception handling• Byte code verification


10


Java is Secure

• With robustness• Bytecode verifier

• Class loader

• Sandbox model

• Digital signature


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Java is Architecture Neutral

Java Source

Java Compiler

Java Byte Code

network

Bytecode

Verifier

Class

Loader

JIT compiler

Interpreter

Runtime

hardware

Compile time

Runtime


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Java is Portable

• Architecture independent

• Ints are always Ints and are always 32-bits 2’s

complemented integers.

• User interfaces via an abstract window system

so the windows can be implemented on UNIX,

PC and Mac


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Java is Multithreaded

• Many simultaneous activities in “one” program

• Better interactive performance

• Better real-time behavior


14


Java is Dynamic.

• Code can be added to a running program – useful in evolving environment

• Reflection capability– to analyze objects in runtime


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Applying Java

• Java Application– Stand-alone program– Java interpreter executes applications

• Java Applet– Java code embedded in HTML documents– Java-enabled browser executes(interprets) applets

• Java Servlet– Web component that generates dynamic content– Run by a web server

• Java Server Page(JSP)– To develop dynamic web pages– a JSP page is an HTML page that contains java code– Run by a web server


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Java Application

• Sample application

class HelloWorldApp {

public static void main (String args[]) {

System.out.println (“Hello World!”);

}

}


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Compile and Execute

• Java compiler generates Java bytecode

• Java interpreter executes Java bytecode

Java Program

Java Classes(Bytecodes)

Java Compiler

Java Interpreter

Results


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Java Applet

• Sample HTML

<html>

<applet code=HelloWorld.class width=100

height=100 >

</applet>

</html>

WebBrowser

Applet(Java classes)

HTML

Web Server

1. load HTML2. load applet3. run applet

1

2


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Java Programming Environment

• Java 2 Standard Edition(J2SE) SDK


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Advanced Java Technology

• Java Beans• Java IDL• Jini technology• Java Message System(JMS)• Enterprise Java Beans(EJB)• Java Server Pages(JSP)• ...

introduction to java kiyeol ryu java programming language

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