/*************************************************************************
* Name:
* NetID:
* Precept:
*
* Description: Creates a bouncing ball animation.
*
* Note: This version differs from the one in Booksite 1.5 in the initial
* position of the ball, and random factors for the velocity and radius.
*************************************************************************/
public class BouncingBall {
// everything is in main() as this is not an object-oriented program
public static void main(String[] args) {
// initialize standard drawing
StdDraw.setXscale(-1.0, 1.0);
StdDraw.setYscale(-1.0, 1.0);
StdDraw.enableDoubleBuffering();
// initial values, random velocity and size
double rx = 0.0, ry = 0.0; // position
double vx = 0.015 - Math.random() * 0.03; // x velocity
double vy = 0.015 - Math.random() * 0.03; // y velocity
double radius = 0.025 + Math.random() * 0.05; // size
// main animation loop
while (true) {
// bounce off wall according to law of elastic collision
if (Math.abs(rx + vx) > 1.0 - radius) vx = -vx;
if (Math.abs(ry + vy) > 1.0 - radius) vy = -vy;
// update position
rx = rx + vx;
ry = ry + vy;
// clear the background
StdDraw.clear(StdDraw.GRAY);
// draw ball on the screen
StdDraw.setPenColor(StdDraw.BLACK);
StdDraw.filledCircle(rx, ry, radius);
// display and pause for 20 ms
StdDraw.show();
StdDraw.pause(20);
}
}
}