QuickStart Java                                  

by Dr. Tom Way

Step-by-step instructions for learning to program in Java

 About the language                                                    

Step 1. Download and install the latest JDK

• SKIP this step if you already have a fairly recent JDK installed.
• Go to the Java website (http://java.sun.com/j2se/1.5.0/download.jsp), save the JDK 5.0 Update to your computer (look for the Windows Offline Installation .exe file).
• Read the installation instructions, if you think you need them.
• Run the installer and "follow your nose"
• Go back and read the installation instructions, and do what it says regarding setting the PATH variable, or for other troubleshooting.

Step 2. Download and install the latest version of Eclipse

• Go to Eclipse website (http://eclipse.org/downloads), and save the zip file to your computer
• Unzip it to a final directory resting place (e.g., C:\eclipse)
• Create a desktop shortcut to it, by doing this:
  • Navigate to the eclipse directory
  • Right-click on eclipse.exe
  • Send To -> Desktop (create shortcut) )
• There are many other IDEs like Eclipse, but it is free, written in Java itself, and very popular.

Step 3. Write a "hello world" program

• Start Eclipse (double-click on the shortcut)
• File->New->Project, select the "Java Project" and click "Next"
• Name the project "Hello World" and click "Finish"
• Right-click on this new project, and select New->Class
• Name the class "HelloWorld" (no spaces)
• Check the box labeled "public static void main(String[] args)
• Inside the main method, add one line, so it looks like this:

public class HelloWorld {

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

• Look for red bars that indicate syntax error, fix (make it match program above)
• Save the program (Eclipse may have already saved it for you)

Step 4. Run the "hello world" program

• Right-click on the "HelloWorld.java" class in the "Package Explorer" on the left
• Select Run As->Java Application
• Watch output in Console at bottom which should print:  Hello world!
• Congratulations!

Step 5. Make it visual

• Modify your program to match this:

  import javax.swing.*;
  
  public class HelloWorld {
  
     public static void main(String[] args) {
  int i = JOptionPane.showConfirmDialog(null,
           "Hello world", "Say hello?",
           JOptionPane.YES_NO_OPTION);
        if (i == JOptionPane.YES_OPTION)
        {
           System.out.println("Hello world!");
        }
     }
  }

• Run as before, and notice "Hello world" is printed only when you click "Yes"!

Step 6. Explore the possibilities

• The JDK you installed came with a variety of excellent demo programs, located in the "demo" subdirectory (e.g., C:\Program Files\Java\jdk1.5.0_04\demo).
• Try changing to the "demo\jfc\SwingSet2" subdirectory.  Run SwingSet2 by double-clicking on the SwingSet2.jar file.  This demo program will show you a wide variety of user interface components that you can use, along with the source code.
• Try this slightly more involved program by creating a new project and copying this code into it:

import javax.swing.*;
import java.util.*;
import java.lang.*;

public class BubbleSort
{
   final private int N = 10;
   private String names[];
   private static Random rng = new Random();

   public BubbleSort()
   {
      initArray();
      printArray("Unsorted");
      sortArray();
      printArray("Sorted");
   }
	
   private void initArray()
   {
      names = new String[N];
      for (int i=0; i<N; i++)
      {
         names[i] = randomWord();
      }		
   }
	
   private void sortArray()
   {
      String temp;
      boolean swapped = true;
      while (swapped)
      {
         swapped = false;
         for (int i=1; i<N; i++)
         {
            if (names[i-1].compareTo(names[i]) > 0)
            {
               temp = names[i-1];
               names[i-1] = names[i];
               names[i] = temp;
               swapped = true;
            }
         }
      }
   }
	
   private void printArray(String type)
   {
      System.out.println(type + " array of " + N + " words");
      Object o[] = new Object[2];
      for (int i=0; i<N; i++)
      {
         System.out.println((i+1)+" "+names[i]);
      }
   }

   public String randomWord()
   {
      return randomString(5,5);
   }

   public String randomString(int lo, int hi)
   {
      int n = rand(lo, hi);
      byte b[] = new byte[n];
      for (int i = 0; i < n; i++)
      {
            b[i] = (byte)rand('a', 'z');
      }
      return new String(b);
   }

   public static int rand(int lo, int hi)
   {
      int n = hi - lo + 1;
      int i = rng.nextInt() % n;
      if (i < 0)
      {
         i = -i;
      }
      return lo + i;
   }

   public static void main(String[] args)
   {
      BubbleSort bs = new BubbleSort();
   }
}

 Learning more                                                        

There is a vast amount of information available on the Internet.  Some of the best sources are:

• JDK API - Find out all of the built-in Java features by looking at the API, which you can view online or download to your computer.
• Java Developers Almanac - Many useful code examples from the book of the same name.
• The Java Tutorial - Sun's excellent practical guide for learning to program in Java.
• JDK Tools and Utilities - Info about all of the nifty tools & utilities that come with the JDK.

 QuickStart Presentation                                           

Download and view the QuickStart Java PowerPoint Presentation.

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