Sample Java Programs

/* This is my first program, it is designed to
demonstrate a simple program structure 
Author: Ramneet Singh
*/

import java.io.*;

class MyFirst
{	
	public static void main(String[ ] args)
	{	
		System.out.println (" Dear Friends, Sat Shri Akal!!");
	}
}

import java.io.*;

class payCheck
{	
	public static void main(String[ ] args)
	{
		double mySalary, myBaseSalary, myOverTime, hourlyRate;
		int hours;

		myBaseSalary = 10000;         
		hourlyRate = 5.50;
		hours = 10;

		// well use a control structure to check for overtime payments
		if ( hours > 0 ) 
			{
				myOverTime = hourlyRate * hours;
				mySalary = myBaseSalary + myOverTime;
			} // end if
		else     
			{
				mySalary = myBaseSalary;
			} // end else

		// Now print out the result
		System.out.println (" Your salary this week is: " +  mySalary);
	} // end method definition

} // Leave a space behind end class bracket so we can easily tell it apart

import java.io.*;

class MyFinance
{	
	public static void main(String[ ] args)
	{
		// declare storage for variables
		double mySalary, myExpenses, myOverdraft, mySaving, surplus;
		int years;
		// initialise variables
		mySalary = 10000;         
		myExpenses = 9500;
		myOverdraft = 20000;
		mySaving = 0;
                    	years = 0;
	
		//calculate a value for surplus
		surplus = mySalary - myExpenses;

		// test for the condition then execute block
		while ( mySaving < myOverdraft )
			{ 
				mySaving = mySaving + surplus;
				years++;
                                   }			

			// print out the result
		System.out.println (" It is going to take you " + years + 								"years to pay off your overdraft! ");
	}

}

import java.io.*;

class flatBroke
{	
	public static void main(String[ ] args)
	{
		for ( int i =10; i>0; i-- )
                                   {
				System.out.println( "Pounds left: œ" + i );
			} // end actions depending on counter			 
		System.out.println( " Flat Broke!" );			
	} // end method

} // end class definition

import java.io.*;

class MyFinance
{	
	public static void main(String[ ] args)
	{
		double mySalary, myExpenses, myOverdraft, mySaving, surplus;
		int years;

		mySalary = 10000;         
		myExpenses = 9500;
		myOverdraft = 20000;
		mySaving = 0;
                    	years = 0;
	
		//calculate a value for surplus
		surplus = mySalary - myExpenses;
                                    
                       // cast mySalary to int for switch statement
                       int payCheck = (int)mySalary;

		//check salary and issue cautionary warning!
		switch ( payCheck )
			{
				case 10000:
				System.out.println (" One day you will earn more 								money!"); 
				break;
				
				case 15000:
				System.out.println (" 15000 is not a bad salary..."); 
				break;

				case 20000:
				System.out.println (" You shouldn't really have an 								overdraft!"); 
				break;

				default:
				// no default behaviour needed, we only need 3 						// messages
				break;
			} // end switch statement
				
			//test for the condition then execute block
		while ( mySaving < myOverdraft )
			{
				mySaving = mySaving + surplus;
				years++;
                                   } // end while

		// print out the result
		System.out.println (" It is going to take you " + years + 								"years to pay off your overdraft! ");
	} // end method
		
} // end clss definition

import java.io.*;

class methods
{
     	public static void main( String[ ] args )
           	{
            	int number=4;      // initialises the number to 4      
            	int answer=Square(number);   // calls the method square to 									// deliver a value							Display(answer);    // Displays the value found in answer
           	} 

    	
	public static int Square( int x)    // Takes an integer x as an argument
           	{
            	return x*x;   // returns the result as an integer
           	}

    	
	public static void Display( int a)  // Takes an integer and displays it
           	{
            	System.out.println(" The answer is: " + a);   
           	}
 
}

import java.awt.*;
import java.awt.image.*;
	
abstract class Aeroplane extends Object  
// create an aeroplane template - an  abstract class would never be 			
//instantiated, only used to derive specialised classes from.
{
	// give it some necessary data
	public int speed;                           		
	public int height;
	public int engines;
	public int fuel;
		
	// tell it where it is on the screen
	int x, y;                                          
		
	//construct an object
	Aeroplane( )                                  		
	{
		this.x = 100;
		this.y = 100;
	}

	public abstract void Draw( Graphics g, ImageObserver o );

	public void Fly( )
	{
		.......// as if by magic!
	}

} // end class definition 	


class Airliner extends Aeroplane
{
	public Airliner( )
	{
		super( );
		private int seats;                 
	}

	public void Draw( Graphics g, ImageObserver o );
           {
	 	// Graphics code goes here
	}

}   // ends class definition

	
class Fighter extends Aeroplane
{
	public Fighter( )
	{
		super( );
		private int guns;
	}
		
	public void Draw( Graphics g, ImageObserver o );
	{
		// Graphics code goes here
	}

} // ends class definition

// This is the main class, which declares an instance of address, defined below

import java.io.* ;

public class Contact
{
   	public static void main( String[] args)
   	{
    		String name = "Joe Soap";

		// create new object
    		address a = new address( "10 Downing Street", 
			      		"Westminster","London","England");   				System.out.println("Name= " + name +"Address= "+
						 			a.retrieve( ));
    	}

}

class address
   {
      	private String street;
      	private String city;
      	private String county;
      	private String country;
      		
	// established data storage, now construct class
	// passing it some values as parameters

      	public address( String s, String c, String co, String cou )
      	{
         		street = s;
         		city = c;
         		county = co;
         		country = cou;
     	}
		
	    		
	//provide an accessor method to pass data with
	public String retrieve( )
      	{
         		return street + "," + city + "," + county +"," + country;
      	}
 
} // end class definition

import java.awt.*;

public class Bets extends Frame
{
   	Choice numbers;   // gives us a pull down menu to list the numbers
   	TextField bet;        // holds the actual bet
   
   	public Bets( )                      //construct the object
  	{ 
      		numbers = new Choice( );      // initialise the pull down menu
      		numbers.addItem("1");
      		numbers.addItem("2");
      		numbers.addItem("3");
      		numbers.addItem("4");
      		numbers.addItem("5");
      
      		bet = new TextField(2);        // initialise a Text Field to hold 2 digits
      
      		Panel p = new Panel( );         // initialise a panel to put things on 
      		p.setLayout(new FlowLayout( ));   // get a layout manager
      		p.add(new Button("GO"));      // add a button to the panel
      		p.add(new Label("Stake"));
      		p.add(numbers);
      		p.add(new Label("Bet"));
      		p.add(bet);
      		add("South", p);   // add the panel and all its components at 							// base
      	}
   
             // we need a method to look after our choices 

   	public boolean action(Event e, Object o)   
   	{
    		String result= null;
   		if (e.target.equals(numbers))
        		{
           		 	result = Integer.toString(numbers.getSelectedIndex( )+1 );
            		bet.setText( result);
        		}
    		else if (o.equals("GO"))
         		{
			start( );
		}
         		return true;
   	}
   
   
   	public void start( )
   	{
      			//Insert code here to start race
   	}
  
           // what happens if we close the window?
	public boolean handleEvent(Event e)
   	{
    		if (e.id == Event.WINDOW_DESTROY)
       		System.exit(0);
     		else return super.handleEvent(e);
     		return true;
  	}
   
   	public static void main(String[] args)
   	{
      		Frame f = new bets( );   //declare and initialise a Frame
      		f.resize(300, 100);           // how big is it?
      		f.show( );                        // wheel it on screen!
   	}
	
} // end class definition

import java.awt.*;

public class Calculator extends Frame
{
   	Display out;
   	Keypad in;
   	Maths sums;

   	public Calculator( )
   	{
      		setLayout(new BorderLayout( ));
   
      		out = new Display( );
      		in = new Keypad(out);
      		sums = new Maths(out);
   
      		add("North", out);
      		add("Center", in);
      		add("East", sums);
   	}
   
   	public boolean handleEvent(Event e)
   	{
    		if (e.id == Event.WINDOW_DESTROY)
       		System.exit(0);
     		else return super.handleEvent(e);
     		return true;
  	}
   
   	public static void main(String[] args)
   	{
      		Frame f = new calculator( );
      		f.resize(100, 200);
      		f.show( );
   	} 
   
}


class Display extends Panel
{
   	TextField show;
   
   	public Display( )
      	{
         		show = new TextField(10);
         		Panel p = new Panel( );
         		p.add(show);
         		add ("Center", p); 
     	}
       
   	public void write( String s)
      	{
         		show.setText(s);
      	}
      
   	public String read()
      	{
         		return show.getText();
      	}
   
}


class Keypad extends Panel
{   
      	Display monitor;
      
      	public Keypad(Display mymonitor)
      	{                       
         		monitor = mymonitor;
         		Panel p = new Panel();
         		p.setLayout( new GridLayout(5,3));
      
         		for ( int i = 0; i <= 9; i++)
          			{
				p.add(new Button("" + (char)('0' + i)));
			} 
          		p.add(new Button("."));
          		p.add(new Button(""));
          		p.add(new Button(""));
          		p.add(new Button(""));
          		p.add(new Button("C"));
        
      		add("Center", p);
       	}
       
       	public boolean action(Event e , Object o)
       	{        
               	char c = ((Button) e.target).getLabel().charAt(0);  
               	switch(c)
               	{
                     		case '0':
                     		case '1':
                    	 	case '2':
                     		case '3':
                     		case '4':
                     		case '5':
                     		case '6':
                     		case '7':
                     		case '8':
                     		case '9':
                     		case '.':
                     		monitor.write(monitor.read( ) + c);
                     		break;
                     
                     		case 'C':
                     		monitor.write("");
                    	 	break;
                	}
               	return true;
       	}         
       
}


class Maths extends Panel
{  
   	Display monitor; 
   	double num1, num2, result;
   	char operand;
        
   	public Maths(Display mymonitor )
   	{  
      		monitor = mymonitor;   
      		Panel p = new Panel();
         		p.setLayout( new GridLayout(5,1));
         		p.add(new Button("+"));
         		p.add(new Button("-"));
         		p.add(new Button("*"));
         		p.add(new Button("/"));
         		p.add(new Button("="));
         
         		add("North",p);
   	}
   
   	public boolean action(Event e , Object o)
       	{      
             	char c = ((Button) e.target).getLabel().charAt(0); 
              	switch (c)
              	{
                		case '+':
                		case '*':
                		case '-':
                		case '/':
                		num1 = Double.valueOf(monitor.read( )).doubleValue( );       
                		operand = c;
                
                		monitor.write("");
                		break;
                
                		case '=':  
                		num2 = Double.valueOf(monitor.read( )).doubleValue( );
                		result = sum(num1, num2, operand);                
                		monitor.write(String.valueOf(result));
              	}
      
         	return true;    
       	}
       
       
    	public double sum( double x, double y, char z )
    	{
      		double answer = 0;
      		if ( z == '+') answer = x + y;
      		else if ( z == '-') answer = x - y;
      		else if ( z == '*') answer = x * y;
      		else if ( z == '/') answer = x / y;
      		return answer;
    	}

}

import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
	
//We are going to implement the ActionListener interface
public class myNewButton extends Applet implements ActionListener
{
   	Button b;
   	TextField t;
   	int num, result;
   		
	public void init( )
   	{
      		b = new Button("Double");

		// now associate the ActionListener with the button
      		b.addActionListener(this);

      		t = new TextField(7);
      		t.setText("100");
      
      		add(b);
      		add(t);
   	}
  
  	// ActionListener has only one method - actionPerformed, which we must 				
	// implement
  	public void actionPerformed( ActionEvent e)
   	{
            	num = Integer.parseInt(t.getText());
            	result = num * 2;
            	t.setText( Integer.toString(result));
   	}

}

import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;

public class myNewTwoButtons extends Applet implements ActionListener
{
   	Button b, b1;
   	TextField t;
   	int num, result;
   		
	public void init( )
   	{
      		b = new Button("Double");
      		b.addActionListener(this);
		// set tag for Action Listener to recognise button b by.
		b.setActionCommand("2");
      		b1 = new Button("Treble");
		// the code doesnt require a tag, but it works both ways!
      		b1.addActionListener(this);
      		t = new TextField(7);
      		t.setText("100");
      
      		add(b);
      		add(t);
      		add(b1);
   	}
  
  
  	public void actionPerformed( ActionEvent e)
   	{
            	num = Integer.parseInt(t.getText( ));
            	String s = e.getActionCommand( );
            	if (s == ("2"))
               	{
                  		result = num * 2;
               	}
            	else if (s == ("Treble")
		{
			result = num * 3;
		}
            	t.setText( Integer.toString(result));
   	}

}

import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;

public class myLocalButton extends Applet 
{
   	private ActionListener al;
   	private Button b;
   	private TextField t;
   	private int num, result;
   
	public void init( )
   	{
      		b = new Button("Double");
      		al = new buttonListener( );
      		b.addActionListener(al); 
      		t = new TextField(7);
      		t.setText("100");
      
      		add(b);
      		add(t);
   	}
  
 	class buttonListener implements ActionListener
 	{ 
  		public void actionPerformed( ActionEvent e)
   		{
            		num = Integer.parseInt(t.getText());
            		result = num * 2;
            		t.setText( Integer.toString(result));
   		}
 	}  
 
}

import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;

public class myNewInnerButton extends Applet 
{
   	Button b;
   	TextField t;
  	int num, result;
   	
	public void init( )
   	{
      		b = new Button("Double");
		/* declare and define anonymous inner class, notice the opening 
                                 bracket before new, is not closed until the end of the class definition.*/      				b.addActionListener(new ActionListener( ){
            		public void actionPerformed(ActionEvent e)
               		{
                  			num = Integer.parseInt(t.getText( ));
                  			result = num * 2;
                  			t.setText( Integer.toString(result));  
               		}
		// close both sets of brackets here, class and method call
         		});
     		
		t = new TextField(7);
      		t.setText("100");
      
      		add(b);
      		add(t);
   	}
  
}

import java.awt.*;
import java.awt.event.*;


public class myWindowEvent extends Frame 
{
   	private Button b;
            // constructor for class  
   	public myWindowEvent( )
   	{         
		// create button and attach ActionListener 
      		b = new Button("Quit");
      		b.addActionListener(new ActionListener( ){
         			public void actionPerformed( ActionEvent e )
         			{
            			close( );
         			}
      		});
			
		// we still need to handle the Window Event, but we dont want to 				//implement all seven methods, so we use WindowAdapter      
      		this.addWindowListener(new WindowAdapter( ){
         			public void windowClosing(WindowEvent e)
         			{
            			close( );
         			}
      		});
      
      
      		add(b);
            }
   		
	// method used by both listeners!
   	public void close( )
   	{
      		System.exit(0);
   	}
   
   
   	public static void main(String[] args)
   	{
      		Frame f = new myWindowEvent( );
		// resize is a deprecated method under 1.1, so we use pack( ) instead
      		f.pack( );
      		f.show( );      
   	}
 
}

import java.awt.*;
import java.awt.event.*;
import java.io.*;

public class myMenuEvent extends Frame 
{
   	private Button b;
   	private MenuItem wheat, bacon, eggs, toast;
   	private CheckboxMenuItem hot, iced;

   	public myMenuEvent( )
   	{
      		setLayout(new BorderLayout(20,20));
      			
		// Add button and look after window closing
      		b = new Button("Quit");
      		b.addActionListener(new ActionListener( ){
         			public void actionPerformed( ActionEvent e )
         			{
            			System.exit(0);
         			}
      		});
      
      		this.addWindowListener(new WindowAdapter( ){
         			public void windowClosing(WindowEvent e)
         			{
                			System.exit(0);
         			}
      		});
      			
			// for clarity set up menu first then listeners!
      		MenuBar mb = new MenuBar();
      		this.setMenuBar(mb);
      		Menu Breakfast = new Menu("Breakfast");
      		Menu coffee = new Menu("Coffee");
      		mb.add(Breakfast);
      		Breakfast.add(wheat = new MenuItem("Cereal"));
      		Breakfast.add(bacon = new MenuItem("Rashers"));
      		Breakfast.add(eggs = new MenuItem("Eggs"));
			// coffee is clickable submenu
         			coffee.add(hot = new CheckboxMenuItem("Hot"));
         			coffee.add(iced = new CheckboxMenuItem("Iced"));
      		Breakfast.add(coffee);
      		Breakfast.add(toast = new MenuItem("Toast"));
      
		// now do all the listeners!
      		wheat.addActionListener(new ActionListener( ){
            		public void actionPerformed(ActionEvent e)
               		{
                  			message("Cereal");
               		}
         		});
         
      		bacon.addActionListener(new ActionListener( ){
            		public void actionPerformed(ActionEvent e)
               		{
                  			message("Rashers");
               		}
         		});
      
      		eggs.addActionListener(new ActionListener( ){
            		public void actionPerformed(ActionEvent e)
               		{
                 			message("Eggs");
               		}
         		});
      
      		toast.addActionListener(new ActionListener( ){
            		public void actionPerformed(ActionEvent e)
               		{
                  			message("Toast");
               		}
         		});
         		
		// set state of other option to unchecked if hot is chosen, you
		// cannot have iced hot coffee!
      		hot.addItemListener(new ItemListener( ){
            		public void itemStateChanged(ItemEvent e)
               		{
                  			if(hot.getState( )==true)
                  			message("Hot Coffee");
                  			iced.setState(false);
               		}
         		});
         				
		// use getState to see if it has been clicked on or off
      		iced.addItemListener(new ItemListener( ){
            		public void itemStateChanged(ItemEvent e)
               		{
                  			if(iced.getState( )==true)
                  			message("Iced Coffee");
                  			hot.setState(false);
               		}
         		});
         
      		add(b);     
   		}

    		// you didnt expect a cooked breakfast did you?
   		void message(String s)
   		{
      			System.out.println("You have chosen: " + s);
   		}
   
   
   		public static void main(String[] args)
   		{
      			Frame f = new myMenuEvent( );
      			f.pack( );
      			f.show( );
   		}

}

import java.awt.*;
import java.awt.event.*;

public class myNewDialog extends Frame 
{
   	private Button b;
   	private MenuItem about;
   
   	private About a;

   	public myNewDialog( )
  	{
      		setLayout(new BorderLayout(20,20));
     		b = new Button("Quit");
      		b.addActionListener(new ActionListener( ){
         			public void actionPerformed( ActionEvent e )
         			{
            			System.exit(0);
         			}
      		});
      
      		this.addWindowListener(new WindowAdapter( ){
         			public void windowClosing(WindowEvent e)
         			{
                			System.exit(0);
         			}
      		});
      
      		MenuBar mb = new MenuBar( );
      		this.setMenuBar(mb);
      		Menu Help = new Menu("Help");
		mb.add(Help);
      		Help.add(about = new MenuItem("About"));
         
    		about.addActionListener(new ActionListener( ){
            		public void actionPerformed(ActionEvent e)
               		{
                  			a = new About(myNewDialog.this);
                  			a.show( );
               		} 
         		});
             
      		add(b);     
   	}
   
    	public static void main(String[] args)
   	{
      		Frame f = new myNewDialog( );
     		f.pack( );
      		f.show( );
   	 }
  

}


class About extends Dialog
{
   	private Button b;
   	private Label l, l1;
   	private Panel p, p1;
   
   	public About(Frame parent)
   	{
      		super(parent, "About", false);
      		b = new Button("OK");
      		p = new Panel( );
      		p1 = new Panel( );
      		l = new Label("Teach Yourself Java");
      		l1 = new Label("Chris Wright");
      
      		p.add(l);
      		p.add(l1);
      		p1.add(b);
      
      		b.addActionListener(new ActionListener( ){
         			public void actionPerformed( ActionEvent e )
         			{
            			dispose( );
         			}
      		});
      
      		this.addWindowListener(new WindowAdapter( ){
         			public void windowClosing(WindowEvent e)
         			{
            			dispose( );
         			}
      		});
      
      		add("Center", p);
      		add("South", b);
      		pack( );
      		show( );
   	}

}

import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;

public class myNewCoordinates extends Applet
{
   	private int lastX, lastY;
   	private Color myColor = Color.blue;
    
   	public void init( )
   	{
      		this.setBackground(Color.red);

      		this.addMouseListener(new MouseAdapter( ){
         			public void mousePressed(MouseEvent e)
         			{
            			lastX = e.getX( );
            			lastY = e.getY( );
         			}
      		});
      			
		this.addMouseMotionListener(new MouseMotionAdapter( ){
         			public void mouseDragged(MouseEvent e)
         			{
            			Graphics g = myNewCoordinates.this.getGraphics();
            			g.setColor(myColor);
            			int x = e.getX( );
            			int y = e.getY( );
            			g.drawLine( lastX, lastY, x, y );
            			lastX = x;
            			lastY = y;
            			showStatus("Mouse is at: ("+ lastX+"," + lastY+")");
         			} // end mouseDragged
     		}); // end inner class 
   	} // end init( )
   	
} // end class definition

import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;

public class myInnerScroll extends Applet
{
   	Private Panel p;
   	Private Scrollbar Temp;
   	Private Label CentLabel, FarLabel;
   	Private TextField Centin, Farout;
   	Private int f, c, answer;
   
   
   	public void init( )
   	{  
      		setLayout(new BorderLayout( ));
      
      		Temp = new Scrollbar(Scrollbar.HORIZONTAL, 0, 20, -50, 150);
      		Temp.addAdjustmentListener(new AdjustmentListener( ){
         			public void adjustmentValueChanged(AdjustmentEvent e)
         			{
            			int Scroll;
            			Scroll = Temp.getValue( );
            			convert(Scroll);
         			}
      		}); 
      		
		CentLabel = new Label("Degrees Centigrade");
      		FarLabel = new Label("Degrees Farenheit");
      		Centin = new TextField (5);     
      		Farout = new TextField(5);
      		setBackground(Color.lightGray);
      
      		p = new Panel( );
      		p.add(CentLabel);
      		p.add(Centin);
      		p.add(FarLabel);
      		p.add(Farout);
      
      		add("Center", p);
      		add("South", Temp);
      		Centin.setText("0");
      		Farout.setText("32");
   	}
      
   	public int calc( int x )
   	{
      		answer=(((9 * x)/5) + 32 );
      		return answer;
   	}
   
   	public void convert( int x)
   	{
      		System.out.println("Temp Centigrade is:"+ x);
      		Centin.setText(Integer.toString(x));
      		f = calc(x );
      		Farout.setText( Integer.toString( f ));
   	}

}