public class Bounce
class Ball
class BallPanel extends JPanel
class BounceFrame extends JFrame
1: /**
2: @version 1.32 2004-07-27
3: @author Cay Horstmann
4: */
5:
6: import java.awt.*;
7: import java.awt.event.*;
8: import java.awt.geom.*;
9: import java.util.*;
10: import javax.swing.*;
11:
12: /**
13: Shows an animated bouncing ball.
14: */
15: public class Bounce
16: {
17: public static void main(String[] args)
18: {
19: JFrame frame = new BounceFrame();
20: frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
21: frame.setVisible(true);
22: }
23: }
24:
25: /**
26: A ball that moves and bounces off the edges of a
27: rectangle
28: */
29: class Ball
30: {
31: /**
32: Moves the ball to the next position, reversing direction
33: if it hits one of the edges
34: */
35: public void move(Rectangle2D bounds)
36: {
37: x += dx;
38: y += dy;
39: if (x < bounds.getMinX())
40: {
41: x = bounds.getMinX();
42: dx = -dx;
43: }
44: if (x + XSIZE >= bounds.getMaxX())
45: {
46: x = bounds.getMaxX() - XSIZE;
47: dx = -dx;
48: }
49: if (y < bounds.getMinY())
50: {
51: y = bounds.getMinY();
52: dy = -dy;
53: }
54: if (y + YSIZE >= bounds.getMaxY())
55: {
56: y = bounds.getMaxY() - YSIZE;
57: dy = -dy;
58: }
59: }
60:
61: /**
62: Gets the shape of the ball at its current position.
63: */
64: public Ellipse2D getShape()
65: {
66: return new Ellipse2D.Double(x, y, XSIZE, YSIZE);
67: }
68:
69: private static final int XSIZE = 15;
70: private static final int YSIZE = 15;
71: private double x = 0;
72: private double y = 0;
73: private double dx = 1;
74: private double dy = 1;
75: }
76:
77: /**
78: The panel that draws the balls.
79: */
80: class BallPanel extends JPanel
81: {
82: /**
83: Add a ball to the panel.
84: @param b the ball to add
85: */
86: public void add(Ball b)
87: {
88: balls.add(b);
89: }
90:
91: public void paintComponent(Graphics g)
92: {
93: super.paintComponent(g);
94: Graphics2D g2 = (Graphics2D) g;
95: for (Ball b : balls)
96: {
97: g2.fill(b.getShape());
98: }
99: }
100:
101: private ArrayList<Ball> balls = new ArrayList<Ball>();
102: }
103:
104: /**
105: The frame with panel and buttons.
106: */
107: class BounceFrame extends JFrame
108: {
109: /**
110: Constructs the frame with the panel for showing the
111: bouncing ball and Start and Close buttons
112: */
113: public BounceFrame()
114: {
115: setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
116: setTitle("Bounce");
117:
118: panel = new BallPanel();
119: add(panel, BorderLayout.CENTER);
120: JPanel buttonPanel = new JPanel();
121: addButton(buttonPanel, "Start",
122: new ActionListener()
123: {
124: public void actionPerformed(ActionEvent event)
125: {
126: addBall();
127: }
128: });
129:
130: addButton(buttonPanel, "Close",
131: new ActionListener()
132: {
133: public void actionPerformed(ActionEvent event)
134: {
135: System.exit(0);
136: }
137: });
138: add(buttonPanel, BorderLayout.SOUTH);
139: }
140:
141: /**
142: Adds a button to a container.
143: @param c the container
144: @param title the button title
145: @param listener the action listener for the button
146: */
147: public void addButton(Container c, String title, ActionListener listener)
148: {
149: JButton button = new JButton(title);
150: c.add(button);
151: button.addActionListener(listener);
152: }
153:
154: /**
155: Adds a bouncing ball to the panel and makes
156: it bounce 1,000 times.
157: */
158: public void addBall()
159: {
160: try
161: {
162: Ball ball = new Ball();
163: panel.add(ball);
164:
165: for (int i = 1; i <= STEPS; i++)
166: {
167: ball.move(panel.getBounds());
168: panel.paint(panel.getGraphics());
169: Thread.sleep(DELAY);
170: }
171: }
172: catch (InterruptedException e)
173: {
174: }
175: }
176:
177: private BallPanel panel;
178: public static final int DEFAULT_WIDTH = 450;
179: public static final int DEFAULT_HEIGHT = 350;
180: public static final int STEPS = 1000;
181: public static final int DELAY = 3;
182: }
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