/*

* 模拟小球和墙发生弹性碰撞运动

*/

public class BouncingBalls {

public static void main(String[] args) {

int N = 1;

Ball[] balls = new Ball[N];

for(int i=0;i<N;i++)

balls[i] = new Ball();

while(true)

{

StdDraw.clear();

for (int i = 0; i < balls.length; i++) {

balls[i].move(0.5);

balls[i].draw();

}

StdDraw.show(50);

}

}

}

class Ball {

private double rx,ry;

private double vx,vy;

private final double radius = 0.01;

public Ball()

{

rx = 0.5;

ry = 0.5;

vx = 0.05;

vy = 0.02;

}

public void move(double dt) {

if ((rx + vx*dt < radius) || (rx + vx*dt > 1.0 - radius)) { vx = -vx; }

if ((ry + vy*dt < radius) || (ry + vy*dt > 1.0 - radius)) { vy = -vy; }

rx = rx + vx*dt;

ry = ry + vy*dt;

}

public void draw()

{

StdDraw.filledCircle(rx, ry, radius);

}

}