CSC153, Class 30: Starting Java (once again)

Overview:
* About Java
* A simple Java program
* Java in the MathLAN
* Lab

Notes:
* Food! (For visitors, too.)
  (Sorry about the politically incorrect source)
* Read lab J2 for Wednesday
* Update to syllabus
* Extra credit for Zuk convo and/or talk
* Questions on exam 2?

What is Java?
* Java is an object-oriented programming language
  Used to create computer programs
* Java was developed at Sun Microsystems in mid-1990's
* The future of computing is ...
  + Embedded systems
  + Large-scale systems
* No language is currently good enough for either task: 
  + Easy for programmers to do stupid things
  + Insufficient modularity for large programs
  + Ad-hoc libraries and naming systems
* Solution: Build it ourselves
* In the mid 1990's, the Web was becoming one of the
  dominant computing applications.
  + Problem: Mostly data; little programming
* Enter marketing: Our embedded language can be the 
  language for the Web, as long as we give it a cool-enough
  name.
* Special aspects of Java:
  + Designed as a portable language.  The same Java program
    should run the same (except for speed) on any 
    Java-enabled computer.
  + Java handles memory management issues for you.
  + Java is "secure"/"sandboxed"
  + Java is object-oriented
  + Java is "small"
  + ON the other hand, the standard Java libraries are *huge*

What does a Java program look like?

(1) Every Java program involves one or more classes.
(2) One of those classes must provide a method named "main".
    This method is the "director" or "starting point".

import java.io.PrintWriter;  // Make "PrintWriter" refer to
                             // java.io.PrintWriter
import java.io.*;	// Do the same for anything in
                        // the java.io "package"
			// DON'T DO THIS; IT'S BAD STYLE
/**
 * Your first Java program.
 *
 * @author Samuel A. Rebelsky
 * @version 1.0 of March 2003
 */
public class Sample
{
  /**
   * Your first procedure.
   */
  public static void main(String[] args)
  {
    PrintWriter out;
    out = new PrintWriter(System.out, true);
    out.println("Hello.");
  } // main(String[])
} // class Sample

How do you do all this?
* Editing: Use gedit or xemacs
* Typing javac:  It may not work for you
export PATH=$PATH:/usr/java/j2sdk1.4.1_01/bin/