Chapter 1: Introducing JAVA

2 Introduction Why JAVA Applets and web applications Very rich GUI libraries Portability (machine independence) A real Object Oriented Language Support International character sets (Unicode)

3 Program Development Editing (any text editor or IDE) Compiling (javac)  Java Object (byte) code JVM interprets that code and translates it to machine language code Try installing SDK then use a simple editor edit, compile and run a simple program. See on-line hand out. Do it for the applet too.

4 OOP in JAVA What is an object? Any thing around us A class is a convenient way to group things It defines a set of variables called class data members (attributes) and a number of functions operating on these attributes (methods) Example: CowboyHat, hatOn=false, putHatOn(), takeHatOff() Encapsulation: Hiding implementation Advantages: less error-prone, easier to maintain

5 JAVA’s Class Library Very very rich Library: –Java.lang, java.io, java.util, javax.swing, java.awt, java.awt.event, etc. To include a library in your program you use the import statement (import java.io.*;) Every Java application contains at least one class that defines the main function, the starting execution point. Its form: (public static void main (String [] args) { })