CS 4773 Object Oriented Systems: Topic 1

CS 4773 Object Oriented Systems

About the course

Syallabus

First Assignment

What the course is not.

What the course is.

What is Java?

Java is a programming language which is

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

and most importantly ...

buzzword-compliant

Java is like C and C++ in a number of ways.

Most notable is what it does not contain:

global variables outside the class hierarchy
goto
pointer arithmetic
malloc and free
system dependent data types
varargs
separate header files
preprocessor
structures
simple types passed by reference
multiple inheritance
operator overloading

Setting up your account

Make sure your path includes:
/usr/local/src/inet/JDK/java/bin

Compile with
javac programname.java

Run applications with
java programname

Run applets with
appletviewer programname.java

This assumes that your java source has an HTML heading as a comment.

Test to see that your path is set correctly by executing:
which javac

Ther result should be:
/usr/local/src/inet/JDK/java/bin/javac

A Hello World application

In a clean directory, create a file called HelloWorld.java:

class HelloWorld {
   public static void main(String args[]) {
          System.out.println("Hello World!");
   }
}

Compile this with:
javac HelloWorld.java

This creates a file called HelloWorld.class

Run this using:
java HelloWorld

The output will be:
Hello World!

A Hello World applet

In a clean directory, create a file called HelloWorld.java:

import java.awt.*;
import java.applet.*;
public class HelloWorldApplet extends Applet {
   public void paint(Graphics g) {
      g.drawString("Hello World!", 20, 20);
   }
}

Compile this with:
javac HelloWorld.java

This creates a file called HelloWorld.class

Run this using:
appletviewer HelloWorld

This will create a window containing:
Hello World!
starting at position with (x,y) coordinates (20,20).

(0,0) is the upper left corner.