1 /*
2 * Bouncing balls - each ball is a different thread with a different
3 * time to sleep.
4 * Adds pause and continue buttons.
5 */
6
7 import java.awt.*;
8 import java.awt.event.*;
9
10 public class BouncePause extends Frame implements ActionListener
11 {
12 private Canvas canvas;
13 // store each thread in an array as it is created
14 private int maxthreads = 100;
15 private Thread[] threadarray = new Thread[maxthreads];
16 private int lastthread = -1;
17
18 // the constructor initializes the frame to be a borderlayout
19 // with a canvas in the center and
20 // four buttons labelled Start, Pause, Continue, and Close in the south
21
22 public BouncePause()
23 { setLayout(new BorderLayout());
24 setTitle("BouncePause");
25
26 canvas = new Canvas();
27 add(canvas, BorderLayout.CENTER);
28
29 Panel p = new Panel();
30 Button b1 = new Button("Start");
31 b1.addActionListener(this);
32 p.add(b1);
33 Button b3 = new Button("Pause");
34 b3.addActionListener(this);
35 p.add(b3);
36 Button b4 = new Button("Continue");
37 b4.addActionListener(this);
38 p.add(b4);
39 Button b2 = new Button("Close");
40 b2.addActionListener(this);
41 p.add(b2);
42 add(p, BorderLayout.SOUTH);
43 }
44
45 // responds to the Start button by creating a new instance
46 // of the BallTimes class and starting its thread,
47 // stores each thread in an array of threads
48 // responds to the Pause button by calling thread method suspend
49 // on all the threads
50 // responds to the Continue button by calling thread method resume
51 // on all the threads
52 // responds to the Close button by exiting the application
53
54
55 public void actionPerformed(ActionEvent evt)
56 { if (evt.getActionCommand().equals("Start"))
57 { if (lastthread < (maxthreads - 1))
58 { lastthread++;
59 BallTimes b = new BallTimes(canvas);
60 threadarray[lastthread] = b;
61 b.start();
62 }
63 }
64 else if (evt.getActionCommand().equals("Pause"))
65 { for (int i = 0; i <= lastthread; i++)
66 threadarray[i].suspend();
67 }
68 else if (evt.getActionCommand().equals("Continue"))
69 { for (int i = 0; i <= lastthread; i++)
70 threadarray[i].resume();
71 }
72 else if (evt.getActionCommand().equals("Close"))
73 System.exit(0);
74 }
75
76 // the main method creates an instance of this class and sets the
77 // properties of the frame
78 public static void main(String[] args)
79 { Frame f = new BouncePause();
80 f.setSize(400, 300);
81 f.setVisible(true);
82 }
83
84 }
85
86 /* The BallTimes class is a subclass of Thread, so each instance inherits
87 * thread methods start, stop, sleep, etc.
88 * The run method of the thread loops to draw a ball in a new location
89 * for a fixed number of iterations.
90 * This example has an additional variable sleeptime, which is used to
91 * sleep inbetween iterations.
92 * Note that this class is unchanged from BounceTimes.java example.
93 */
94
95 class BallTimes extends Thread
96 {
97 private Canvas box;
98 private static final int XSIZE = 10;
99 private static final int YSIZE = 10;
100 private int x = 0;
101 private int y = 0;
102 private int dx = 2;
103 private int dy = 2;
104 private int sleeptime;
105
106 // the constructor initializes the canvas to that of the frame
107 // and initializes sleeptime to a random number between 4 and 44
108 public BallTimes(Canvas c)
109 { box = c;
110 sleeptime = ((int)(Math.random() * 40)) + 4;
111 }
112
113 // draws the ball in the current location
114 public void draw()
115 { Graphics g = box.getGraphics();
116 g.fillOval(x, y, XSIZE, YSIZE);
117 g.dispose();
118 }
119
120 // increments the location of the ball, checks the boundary to see
121 // if it should "bounce", and draws the ball
122 public void move()
123 { Graphics g = box.getGraphics();
124 g.setXORMode(box.getBackground());
125 g.fillOval(x, y, XSIZE, YSIZE);
126 x += dx;
127 y += dy;
128 Dimension d = box.getSize();
129 if (x < 0) { x = 0; dx = -dx; }
130 if (x + XSIZE >= d.width) { x = d.width - XSIZE; dx = -dx; }
131 if (y < 0) { y = 0; dy = -dy; }
132 if (y + YSIZE >= d.height) { y = d.height - YSIZE; dy = -dy; }
133 g.fillOval(x, y, XSIZE, YSIZE);
134 g.dispose();
135 }
136
137 // loops for 1000 times and moves the ball
138 public void run()
139 { draw();
140 for (int i = 1; i <= 1000; i++)
141 { move();
142 try { Thread.sleep(sleeptime); } catch(InterruptedException e) {}
143 }
144 }
145 }
146
147
148