JJ Game Programming Java Examples

GuessColor An easy game to play and modify (View the code)
MemoryGame (WARNING: Advanced code) arrays of objects (View the code)
GraphicDisplayOfFontStyleAndSize Display text graphics (there are no buttons, just a static graphics message for you) (View the code)
GraphicDisplayOfTextFieldContents TextField and Graphics (View the code)
GraphicDisplayOfMouseClickLocation Locate mouse click (View the code)
MoveBlueSquareToMouseClick Mouse click moves blue square (View the code)
WhatADrag Click and drag blue square (View the code)
BlueBallInBox (WARNING: Longer example) Snap blue ball into box (View the code)
BothGraphicsAndButtonsInJJ (WARNING: Nested classes) Both Graphics and Buttons (View the code)

Java Source Code for above game programming examples

1. GuessColor

// A simple guessing game.
// After playing the game,
// modify the String values
// to create your own game.

import java.awt.*;

class GuessColor extends JJAppletWithButtons {
private Button b1, b2, b3, b4, b5, b6;
private TextField tfBottom;

//You must write an init()
//which is called when the JJApplet is opened
 public void init() {
  setupLocationOfButtonsAndSuch();
 }

//The name of this method is whatever you want
 //OR
 //all this code could have been in the init() method
 private void setupLocationOfButtonsAndSuch() {
  JJGridPanel pButtons2by3;
  JJBorderPanel p;
   p = getMasterBorderPanel();
   pButtons2by3 = new JJGridPanel(2,3);

b1 = new Button("red");
   b2 = new Button("orange");
   b3 = new Button("yellow");
   b4 = new Button("green");
   b5 = new Button("blue");
   b6 = new Button("purple");
   pButtons2by3.add(b1);
   pButtons2by3.add(b2);
   pButtons2by3.add(b3);
   pButtons2by3.add(b4);
   pButtons2by3.add(b5);
   pButtons2by3.add(b6);

tfBottom = new TextField("Please guess a color");

p.add("North", new Label("Pick a color, any color"));
   p.add("Center", pButtons2by3);
   p.add("South", tfBottom);
 }

// If you extend JJAppletWithButtons, you need to
 // write this handleButtonPress void method that
 // is passed one Button value
 public void handleButtonPress(Button b) {
  String replyText;
   if (b == b1) {
      replyText = "Not yet, please guess again";
   } else if (b == b2) {
      replyText = "Almost, guess again";
   } else if (b == b3) {
      replyText = "Nope, guess once more";
   } else if (b == b4) {
      replyText = "Incorrect guess, try again";
   } else if (b == b5) {
      replyText = "No, keep guessing";
   } else { // (b == b6)
      replyText = "YOU GUESSED IT!!!";
   }
   tfBottom.setText(replyText);
 } //end handleButtonPress
} //end class GuessColor

2. MemoryGame

//JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ
//
// The next step is actually quite a leap.  From the
// simple point-and-click game in the previous step to
// a more involved game:
//  (1) use the setLabel() and getLabel() methods on a
// Button object to change the contents of a button, and
//  (2) use arrays of objects (String and Button arrays)
//
// Play the game first,
// take a look at the code itself second,
// and finally, come up with a more involved game of your
// own now that you have an example of changing the button
// content and how to use arrays in Java.
// It turns out that most people write tic-tac-toe, but
// you can publish any game you wish as your final
// lab assignment.
//
//JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ

import java.awt.*;

class MemoryGame extends JJAppletWithButtons {
// This program introduces two new topics:
//  (1) Using setLabel and getLabel to change the
//      contents(label) of a button, and
//  (2) How to use arrays of objects in Java.
//
// More on (2) is seen below as the String[]
// (read String[] as "String array") box named "pair"
// goes through the three required steps for using
// Java object arrays:
//  (1) Declare the box (a.k.a. "variable") of object
//   array type
//  (2) "New" the array box once you know how many
//   elements you would like to have in the array
//  (3) Finally, for each element in the array, assign
//   it to an object.
//
// Notice that step (3) is not needed for "primitive type"
// arrays (such as int, double, boolean).
// Also note that forgetting either step (2) or (3) is
// likely going to result in a null pointer exception.

private Button[] b;
private String[] pair;   //step 1 of 3, declare String[]
private TextField tfBottom;
private int turnCount;
private int matches;
private String choice1, choice2;
private Button firstButton;
private Button secondButton;
private String sFirstButtonNumber;
private String sSecondButtonNumber;
private boolean gotMatch;

public void init() {
  setupLocationOfButtonsAndSuch();
  pair = new String[16];  //step 2 of 3, allocate size
  turnCount = 0;
  matches = 0;
  choice1 = "if you see me, it is a bug 1";
  choice2 = "if you see me, it is a bug 2";
  doTheShuffle();
}

private void setupLocationOfButtonsAndSuch() {
  JJGridPanel pButtons4by4;
  JJBorderPanel p;
  int i;
   p = getMasterBorderPanel();
   b= new Button[16]; // that is, a 4 by 4
   pButtons4by4 = new JJGridPanel(4, 4);
   for(i=0; i<16; i++) {
    b[i] = new Button(""+i);
    pButtons4by4.add(b[i]);
   }
   tfBottom = new TextField("Pick a card, any card");
   p.add("North", new Label("Play the memory game!"));
   p.add("Center", pButtons4by4);
   p.add("South", tfBottom);
}

public void handleButtonPress(Button b) {
  String didItMatch;
    if ((turnCount % 3) == 0) {
     firstButton = b;
     sFirstButtonNumber = firstButton.getLabel();
     choice1 = getCardValue(firstButton);
     firstButton.setLabel(choice1);
     tfBottom.setText("Now, pick another card");
    } else if ((turnCount % 3) == 1) {
     secondButton = b;
     sSecondButtonNumber = secondButton.getLabel();
     choice2 = getCardValue(b);
     secondButton.setLabel(choice2);
     didItMatch = handleEndOfTurn(choice1, choice2);
     tfBottom.setText(didItMatch);
     if ((didItMatch.substring(0,3)).equals("YES")) {
      matches += 1;
      gotMatch = true;
     } else {
      gotMatch = false;
     }//endif match
    } else {  // assert: (turnCount % 3) == 2
     if (gotMatch) {
     } else {
      firstButton.setLabel(sFirstButtonNumber);
      secondButton.setLabel(sSecondButtonNumber);
     }
     if (matches == 0) {
      tfBottom.setText
("Another turn begins ... pick a card");
     } else if (matches == 1) {
      tfBottom.setText
("Two down, lots to go ... pick a card");
     } else if (matches == 2) {
      tfBottom.setText
("Four down, still lots to go ... pick a card");
     } else if (matches == 3) {
      tfBottom.setText
("Three pairs already! ... pick a card");
     } else if (matches == 4) {
      tfBottom.setText("Almost done ... pick a card");
     } else if (matches == 5) {
      tfBottom.setText("Can you get the rest?");
     } else if (matches == 6) {
      tfBottom.setText("Finish it off");
     } else if (matches == 7) {
      tfBottom.setText("Bob's your uncle");
     } else {
      tfBottom.setText("Play again by clicking cards");
      doTheShuffle();
      matches = 0;
     }
    }//endif
    turnCount += 1;
} //end handleButtonPress

//TEACHERS: You could simply have your students
// fix/play this method.  For now, the game is
//  the same every time.  Actually, this makes for
//   another type of "memory game" ... try to play
//    it every day until you can get all the matches
//     correctly without missing a click.
//      But, to stay on the topic, this method
//       should be fixed to include randomness.
private void doTheShuffle() {
  pair[0] = "5 of Diamonds"; //step 3 of 3, supply a value
  pair[1] = "4 of Clubs";    //step 3 of 3, supply a value
  pair[2] = "7 of Clubs";    //step 3 of 3, ...
  pair[3] = "3 of Diamonds"; //...
  pair[4] = "2 of Spades";
  pair[5] = "9 of Hearts";
  pair[6] = "3 of Spades";
  pair[7] = "8 of Hearts"; //...step 3 of 3, supply a value
  pair[8] = pair[0];
  pair[9] = pair[2];
  pair[10] = pair[1];
  pair[11] = pair[4];
  pair[12] = pair[5];
  pair[13] = pair[3];
  pair[14] = pair[7];
  pair[15] = pair[6];
  b[0].setLabel(pair[0]);
  b[1].setLabel(pair[1]);
  b[2].setLabel(pair[2]);
  b[3].setLabel(pair[3]);
  b[4].setLabel(pair[4]);
  b[5].setLabel(pair[5]);
  b[6].setLabel(pair[6]);
  b[7].setLabel(pair[7]);
  b[8].setLabel(b[0].getLabel());
  b[9].setLabel(b[2].getLabel());
  b[10].setLabel(b[1].getLabel());
  b[11].setLabel(b[4].getLabel());
  b[12].setLabel(b[5].getLabel());
  b[13].setLabel(b[3].getLabel());
  b[14].setLabel(b[7].getLabel());
  b[15].setLabel(b[6].getLabel());

for (int i=0; (i<16); i++) {
     b[i].setLabel(""+i);
  }
}

private String getCardValue(Button b) {
   String sCardNumber;
   String result;
    sCardNumber = b.getLabel();
    result = pair[myStringToInt(sCardNumber)];
    return result;
}

private String handleEndOfTurn(
  String s1,    // their first card
  String s2) {  // their second card
  String result;
   if (s1.equals(s2)) {
     result = "YES, a match. Play some more...";
   } else {
     result = "CLICK ANY CARD: Turn these two back over";
   }
   return result;
}

private int myStringToInt(String s) {
  int result;
  Integer I;
   I = new Integer(s);
   result = I.intValue();
   return result;
}

}//end class MemoryGame

3. GraphicDisplayOfFontStyleAndSize

4. GraphicDisplayOfTextFieldContents

5. GraphicDisplayOfMouseClickLocation

6. MoveBlueSquareToMouseClick

7. WhatADrag

// drag a square around

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

class WhatADrag extends JJAppletWithoutButtons implements MouseListener, MouseMotionListener {
    private int x;
    private int y;
    private Label instructions;

public void init() {
        instructions = new Label("Hold and drag mouse around.");
        add(instructions);
        this.addMouseListener(this);
        this.addMouseMotionListener(this);
        x = 10;
        y = 10;
    }
    public void paint(Graphics g) {
        setBackground(Color.white);
        g.setColor(Color.blue);
        g.fillRect(x, y, 20, 20);
    }
    public void mouseClicked(MouseEvent event) {
    }
    public void mousePressed(MouseEvent event) {
    }
    public void mouseReleased(MouseEvent event) {
    }
    public void mouseEntered(MouseEvent event) {
    }
    public void mouseExited(MouseEvent event) {
    }
    public void mouseDragged(MouseEvent event) {
        x = event.getX();
        y = event.getY();
        repaint();
    }
    public void mouseMoved(MouseEvent event) {
    }
} //end class WhatADrag

8. BlueBallInBox

//place blue ball into a box

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

class BlueBallInBox extends JJAppletWithoutButtons implements MouseListener, MouseMotionListener {
    private int ballX;         // x-value of center of ball
    private int ballY;         // y-value of center of ball
    private int ballSize;      // Size of ball
    private int halfBallSize;  // Half of the ball size (its radius)

private int box1X;         // x-value of upper left corner of first box
    private int box1Y;         // y-value of upper left corner of first box

private int box2X;         // x-value of upper left corner of second box
    private int box2Y;         // y-value of upper left corner of second box

private Color ballColor;
    private boolean ballBeingDragged;  // true if the user is dragging the ball

public void init() {
        this.addMouseListener(this);
        this.addMouseMotionListener(this);
        ballX = 60;
        ballY = 60;
        ballSize = 20;
        halfBallSize = ballSize / 2;

box1X = 50;
        box1Y = 50;
        box2X = 250;
        box2Y = 50;

ballColor = Color.blue;
        ballBeingDragged = false;
    }
    public void paint(Graphics g) {
        setBackground(Color.white);

// Draw the first box
        g.setColor(Color.black);
        g.drawRect(box1X, box1Y, ballSize, ballSize);

// Draw the second box
        g.setColor(Color.black);
        g.drawRect(box2X, box2Y, ballSize, ballSize);

// Draw the ball
        g.setColor(ballColor);
        g.fillOval(ballX - halfBallSize, ballY - halfBallSize, ballSize, ballSize);
    }
    public void mouseClicked(MouseEvent event) {
    }
    public void mouseMoved(MouseEvent event) {
    }
    public void mousePressed(MouseEvent event) {
        int x;
        int y;

x = event.getX();
        y = event.getY();

if ( (x >= ballX - halfBallSize) &&
             (x <= ballX + halfBallSize) &&
             (y >= ballY - halfBallSize) &&
             (y <= ballY + halfBallSize) ) {
            ballBeingDragged = true;

ballX = x;
            ballY = y;

repaint();
        } //end if
    }
    public void mouseDragged(MouseEvent event) {
        if (ballBeingDragged) {
            ballX = event.getX();
            ballY = event.getY();
            repaint();
        } //end if
    }
    public void mouseReleased(MouseEvent event) {
        if (ballBeingDragged) {
            ballX = event.getX();
            ballY = event.getY();

// Check if user released in box 1
            // If so, "snap" the ball into box 1

if ( (ballX >= box1X) &&
                 (ballX <= box1X + ballSize) &&
                 (ballY >= box1Y) &&
                 (ballY <= box1Y + ballSize) ) {
                ballX = box1X + halfBallSize;
                ballY = box1Y + halfBallSize;
            } //end if

// Check if user released in box 2
            // If so, "snap" the ball into box 2

if ( (ballX >= box2X) &&
                 (ballX <= box2X + ballSize) &&
                 (ballY >= box2Y) &&
                 (ballY <= box2Y + ballSize) ) {
                ballX = box2X + halfBallSize;
                ballY = box2Y + halfBallSize;
            } //end if

ballBeingDragged = false;
            repaint();
        } //end if
    }
    public void mouseEntered(MouseEvent event) {
    }
    public void mouseExited(MouseEvent event) {
    }
} //end class BlueBallInBox

9. BothGraphicsAndButtonsInJJ

// Using both buttons and graphics is a bit tricky.
// It requires using an inner class

import java.awt.*;

class BothGraphicsAndButtonsInJJ extends JJAppletWithButtons {
   private Color outsideColor;
   private Color insideColor;
   private Button bOutsideColor;
   private Button bInsideColor;
   private JJBorderPanel p;

private innerClassForGraphic forPainting;

// you must write an init method
    public void init() {
      Panel pForTwoButtons;
       forPainting = new innerClassForGraphic();
       outsideColor = Color.green;
       insideColor = Color.blue;
       p = getMasterBorderPanel();
       bOutsideColor = new Button("New Outside Color");
       bInsideColor = new Button("New Inside Color");
       pForTwoButtons = new JJGridPanel(1,2);
       pForTwoButtons.add(bOutsideColor);
       pForTwoButtons.add(bInsideColor);
       p.add("Center",forPainting);
       p.add("South",pForTwoButtons);
    }

// HANDLE ANY BUTTON PRESS:
    // The button that was pressed is passed into this method
    public void handleButtonPress(Button b) {
       if (b == bOutsideColor) {
          outsideColor = rotateColor(outsideColor);
       } else {
          insideColor = rotateColor(insideColor);
       }
       forPainting.repaint();  // this will call the paint method
    }

private Color rotateColor(Color colorCode) {
      Color result;
       result = Color.white;  // just in case
       if (colorCode==Color.yellow) {
          result = Color.red;
       } else if (colorCode==Color.red) {
          result = Color.blue;
       } else if (colorCode==Color.blue) {
          result = Color.green;
       } else if (colorCode==Color.green) {
          result = Color.cyan;
       } else if (colorCode==Color.cyan) {
          result = Color.magenta;
       } else if (colorCode==Color.magenta) {
          result = Color.orange;
       } else if (colorCode==Color.orange) {
          result = Color.pink;
       } else if (colorCode==Color.pink) {
          result = Color.red;
       } //end if
       return result;
    }

// NEED AN INNER CLASS:
    // 1. Give it any name you want (must match above use of this class)
    // 2. Make sure it extends Panel
    // 3. It must have a paint(Graphics anyNamehere) method

class innerClassForGraphic extends Panel {
       // you must write a paint method
       public void paint(Graphics g) {
        Font italicBold25;
        Font plain36;
         italicBold25 = new Font("SansSerif", Font.BOLD+Font.ITALIC, 25);
         plain36 = new Font("Serif", Font.PLAIN, 36);
         this.setBackground(outsideColor);
         g.setFont(italicBold25);
         g.drawString("Happy Birthday", 30,30);
         g.setColor(insideColor);
         g.fillRect(50,50,140,100);
         g.setColor(Color.white);
         g.setFont(plain36);
         g.drawString("to you", 70,100);
       } //end paint
    } //end class innerClassForGraphic

}//end class BothGraphicsAndButtonsInJJ

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