import java.awt.Color; import java.awt.Cursor; import java.awt.Font; import java

Question

import java.awt.Color;
import java.awt.Cursor;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.util.ArrayList;
import java.util.Iterator;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.WindowConstants;

public class BouncingBalls extends JPanel implements Runnable,
MouseMotionListener, MouseListener {
Thread runner;

Image buffer;
Graphics bufferGraphics;

ArrayList collideBalls = new ArrayList();

ArrayList obstacles = new ArrayList();

boolean intro = true;

OverAction foundAction = null;

public static void main(String[] args) {
JFrame frame = new JFrame("Bouncing Balls");
BouncingBalls clickBall = new BouncingBalls();
frame.getContentPane().add(clickBall);
frame.setSize(500, 500);
frame.setLocation(50, 50);
frame.show();
frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
}

public BouncingBalls() {
//our balls have different start coordinates, increment values
//(speed, direction) and colors
collideBalls.add(new CollideBall(50, 20, 1.5, 2.0, Color.orange, 12));
collideBalls.add(new CollideBall(60, 210, 2.0, -3.0, Color.red, 12));
collideBalls.add(new CollideBall(15, 70, -2.0, -2.5, Color.pink, 12));
collideBalls.add(new CollideBall(150, 30, -2.7, -2.0, Color.cyan, 12));
collideBalls.add(new CollideBall(210, 30, 2.2, -3.5, Color.magenta, 12));
collideBalls.add(new CollideBall(360, 170, 2.2, -1.5, Color.yellow, 12));
collideBalls.add(new CollideBall(210, 180, -1.2, -2.5, Color.blue, 12));
collideBalls.add(new CollideBall(330, 30, -2.2, -1.8, Color.green, 12));
collideBalls.add(new CollideBall(180, 220, -2.2, -1.8, Color.black, 12));
collideBalls.add(new CollideBall(330, 130, -2.2, -1.8, Color.gray, 12));

// Add any obstacles

obstacles.add(new Obstacle(150, 80, 130, 90));

addMouseListener(this);
addMouseMotionListener(this);
addComponentListener(new ComponentAdapter() {
public void componentResized(ComponentEvent e) {
createDoubleBuffer();
}
});

new Thread(this).start();
}

private void createDoubleBuffer() {
if (bufferGraphics != null) {
bufferGraphics.dispose();
}

buffer = createImage(getSize().width, getSize().height);
bufferGraphics = buffer.getGraphics();

}

public void run() {
while (true) {
Thread.currentThread().setPriority(Thread.MAX_PRIORITY);

try {
Thread.sleep(15);
} catch (Exception e) {
}

//move our balls around
for (Iterator iter = collideBalls.iterator(); iter.hasNext();) {
CollideBall collideBall = (CollideBall) iter.next();
collideBall.move(getBounds(), obstacles);
}

handleCollision();

repaint();
}
}
private void handleCollision() {
//we iterate through all the balls, checking for collision
for (Iterator iter1 = collideBalls.iterator(); iter1.hasNext();) {
CollideBall ball1 = (CollideBall) iter1.next();
for (Iterator iter2 = collideBalls.iterator(); iter2.hasNext();) {
CollideBall ball2 = (CollideBall) iter2.next();

if (ball1 != ball2) {
if (collide(ball1, ball2)) {
ball1.hit(ball2);
ball2.hit(ball1);
}
}
}
}
}

private boolean collide(CollideBall b1, CollideBall b2) {
double wx = b1.getCenterX() - b2.getCenterX();
double wy = b1.getCenterY() - b2.getCenterY();

//we calculate the distance between the centers two
//colliding balls (theorem of Pythagoras)
double distance = Math.sqrt(wx * wx + wy * wy);

if (distance < b1.getDiameter())
return true;

return false;
}

public void update(Graphics g) {
paint(g);
}

public void paint(Graphics g) {
if (bufferGraphics == null) {
createDoubleBuffer();
}

bufferGraphics.setColor(Color.lightGray);
bufferGraphics.fillRect(0, 0, getSize().width, getSize().height);

bufferGraphics.draw3DRect(5, 5, getSize().width - 10, getSize().height - 10,
false);

//paint the obstacles rectangle
for (Iterator iter = obstacles.iterator(); iter.hasNext();) {
Obstacle obstacle = (Obstacle) iter.next();
obstacle.paint(bufferGraphics);
}

//paint our balls
for (Iterator iter = collideBalls.iterator(); iter.hasNext();) {
CollideBall ball = (CollideBall) iter.next();
ball.paint(bufferGraphics);
}

if (intro) {
bufferGraphics.setColor(Color.red);

bufferGraphics.setFont(new Font("Helvetica", Font.PLAIN, 12));
bufferGraphics.drawString("You can move and resize the rectangles!", 20,
30);
}

g.drawImage(buffer, 0, 0, this);
}

public void mouseDragged(MouseEvent e) {
if (foundAction != null) {
foundAction.mouseDragged(e);
}
}

public void mouseMoved(MouseEvent e) {
int x = e.getX();
int y = e.getY();

for (Iterator iter = obstacles.iterator(); iter.hasNext();) {
Obstacle obsticle = (Obstacle) iter.next();

OverAction overAction = obsticle.getOverAction(x, y);

if (overAction != null) {
setCursor(overAction.getCursor());
return;
}
}

setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
}

public void mouseClicked(MouseEvent e) {
}

public void mouseEntered(MouseEvent e) {
}

public void mouseExited(MouseEvent e) {
}

public void mousePressed(MouseEvent e) {
int x = e.getX();
int y = e.getY();

for (Iterator iter = obstacles.iterator(); iter.hasNext();) {
Obstacle obsticle = (Obstacle) iter.next();

OverAction overAction = obsticle.getOverAction(x, y);

if (overAction != null) {
overAction.mousePressed(e);
foundAction = overAction;
return;
}
}
}

public void mouseReleased(MouseEvent e) {
foundAction = null;
}
}






4) In the bouncing folder there is a program BouncingBalls.java. Examine it, compile and run it.

a. What is this program doing?


b. Note that you can click and drag the obstacle (i.e., the rectangle) to a new position. Furthermore, if you click and drag the edges or corners of the obstacle, you can resize it. Does resizing work correctly for all edges and corners? (Hint there is something wrong with the behavior of dragging one of the edges or corners). If not, what is the incorrect behavior and for what edge or corner.



c. Change it so that it some of the balls have different size diameters. Recompile and test your changes. (Hint: examine the CollideBall.java source. Look for the constructor and note the arguments. Then in BouncingBalls.java change the size of the diameter argument is a few of the calls where a CollideBall is instantiated, i.e., created)

d. Change it so that is creates and displays a couple more Obstacles. Note you will need to set different coordinates for each Obstacle. Re-compile and test it.

e. Let’s have some fun. Add the following code in the constructor of BouncingBalls after the last line in which a CollideBall is instantiaed:

for (int i = 0; i < 50; i++ ) {
collideBalls.add(
new CollideBall(i * 10, i * 10, -2.2, -1.8, Color.gray, 12));
}

Recompile and test it. What did this do?

Explanation / Answer

import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import javax.swing.ImageIcon; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.WindowConstants; class Dice extends JLabel { private int value; Dice() { super(); setValue(0); addMouseListener(new MouseAdapter() { public void mouseClicked(MouseEvent me) { setValue(getValue() + 1); } }); } public int getValue() { return value; } void setValue(int value) { this.value = value; switch (value) { case 0: this.setIcon(getImage("images\one.GIF")); break; case 1: this.setIcon(getImage("images\two.GIF")); break; case 2: this.setIcon(getImage("images\three.GIF")); break; case 3: this.setIcon(getImage("images\four.GIF")); break; case 4: this.setIcon(getImage("images\five.GIF")); break; case 5: this.setIcon(getImage("images\six.GIF")); break; } } ImageIcon getImage(String name) { Object o = getClass().getResource(name); return new ImageIcon(getClass().getResource(name)); } public static void main(String[] a) { JPanel panel = new JPanel(); Dice dice1 = new Dice(); dice1.setValue(2); panel.add(dice1); JFrame app = new JFrame(); app.getContentPane().add(panel); app.setLocation(300, 200); app.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); app.pack(); app.show(); } }

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