Principles of Object-Oriented Software Development

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Principles of Object-Oriented Software Development

• The language Java

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The language Java
Introduction Terminology
Expressions Control Objects
Inheritance Techniques Summary
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Java -- the dial-tone of the Internet 1995
Introduction at WWW3 1996 1.0 with AWT
1997 1.1.x with modified event handling 1998
version 1.2 (beta) with Swing Design
principles -- safety a modern programming
language ,C syntax, no pointers virtual
machine (runs on many platforms) libraries
threads, networking, AWT downloadable
classes, support for applets extensions and
APIs Beans, Swing, MEDIA, 3D See
http//www.javasoft.com and http//java.sun.com/d
ocs/books/tutorial
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Keywords
Java overview

• new, finalize, extends, implements, synchronized

Language features no pointers -- references
only simplify life garbage collection -- no
programmers' intervention constructors -- to
create and initialize single inheritance --
for refinement interfaces -- abstract classes
synchronized -- to prevent concurrent
invocation private, protected, public -- for
access protection
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Type expressions

• basic types -- int, char, float, ...
• Array -- int arSIZE
• String -- String args
• class -- user-defined

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Expressions

• operators -- , - ,.., lt , lt ,.., , !
  ,.., ,
• indexing -- o e
• access -- o.m(...)
• in/decrement -- o, o--
• conditional -- b?e1e2

Assignment var expression modifying
-- . -, ...
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Control

• conditional -- if (b) S1 else S2
• selection -- switch(n) case n1 S1 break ...
  default ...
• iteration -- while (b) S
• looping -- for( int i 1 i lt MAX i) S
• jumps -- return, break, continue

Java -- control
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Hello World -- Java (1)
public class HelloWorld public static void
main(String args) System.out.println(
"Hello World")
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Hello World - interface public interface World
public void hello() Hello World -
class public class HelloWorld implements World
public void hello()
System.out.println("Hello World")
Java -- objects (2)
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Hello World -- Java (2)
import java.awt.Graphics public class
HelloWorld extends java.applet.Applet
public void init() resize(150,50)
public void paint(Graphics g)
g.drawString("Hello, World!", 50, 25)

Java -- inheritance
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Java -- techniques

• applets -- extend your browser
• servlets -- extend your server
• networking -- urls, sockets
• RMI -- remote method invocation
• reflection -- meta-information
• beans -- component technology
• JNI -- writing native methods
• javadoc -- online class documentation

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The language Java

• design principles -- safety
• terminology -- object, interface
• syntax -- like C
• objects -- abstract data types, interfaces
• inheritance -- single inheritance
• techniques -- dynamic casts, reflection, APIs