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1 import java.awt.*;
2 import java.awt.event.*;
3 import JSci.physics.*;
4
5
10 public final class Rotation extends Frame implements Runnable  {
11 private RigidBody2D body=new RigidBody2D();
12 private Display display=new Display();
13
14 public static void main(String arg[]) {
15 Frame app=new Rotation();
16 app.setSize(250,250);
17 app.setVisible(true);
18 }
19 public Rotation() {
20 super("Rotation!");
21 add(display,"Center");
22 addWindowListener(new WindowAdapter() {
23 public void windowClosing(WindowEvent evt) {
24 dispose();
25 System.exit(0);
26 }
27 });
28 body.setMass(5.0);
29 body.setMomentOfInertia(5.0);
30 Thread thr=new Thread (this);
31 thr.start();
32 }
33 public void run() {
34 double width,height;
35 double x,y;
36 while(true) {
37 body.move(0.01);
38 width=getSize().width;
39 height=getSize().height;
40 x=body.getXPosition();
41 y=body.getYPosition();
42 if(x>width/2.0)
43 body.setXPosition(x-width);
44 else if(x<-width/2.0)
45 body.setXPosition(x+width);
46 if(y>height/2.0)
47 body.setYPosition(y-height);
48 else if(y<-height/2.0)
49 body.setYPosition(y+height);
50 display.repaint();
51 try {
52 Thread.sleep(100);
53 } catch(InterruptedException e) {}
54 }
55 }
56 private final class Display extends Canvas {
57 private Point start,end;
58 private boolean firstDrag=false;
59 public Display() {
60 addMouseListener(new MouseAdapter() {
61 public void mousePressed(MouseEvent e) {
62 firstDrag=true;
63 start=end=null;
64 }
65 public void mouseReleased(MouseEvent e) {
66 if(start!=null && end!=null) {
67 final double Fx=end.x-start.x;
68 final double Fy=-(end.y-start.y);
69 final int cx=getSize().width/2;
70 final int cy=getSize().height/2;
71 final double x=(end.x-cx)-body.getXPosition();
72 final double y=-(end.y-cy)-body.getYPosition();
73 for(int i=0;i<4;i++) {
74 body.applyForce(Fx,Fy,x,y,0.05);
75 body.move(0.05);
76 repaint();
77 }
78 System.out.println("Force ("+Fx+','+Fy+") applied at ("+x+','+y+')');
79 }
80 }
81 });
82 addMouseMotionListener(new MouseMotionAdapter() {
83 public void mouseDragged(MouseEvent e) {
84 if(firstDrag) {
85 start=e.getPoint();
86 firstDrag=false;
87 } else if(start!=null)
88 end=e.getPoint();
89 }
90 });
91 }
92 public void paint(Graphics g) {
93 final Graphics2D g2=(Graphics2D)g;
94 final int cx=getSize().width/2;
95 final int cy=getSize().height/2;
96 final double x=body.getXPosition();
97 final double y=body.getYPosition();
98 g2.translate(x,-y);
99 g2.rotate(-body.getAngle(),cx,cy);
100 g2.setColor(Color.red);
101 g2.fillRect(cx-50,cy-10,100,20);
102 }
103 public Dimension getPreferredSize() {
104 return new Dimension(200,200);
105 }
106 }
107 }
108
109
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Java API By Example, From Geeks To Geeks.