DeluxeBouncingBall.java

Below is the syntax highlighted version of DeluxeBouncingBall.java from §1.5 Input and Output.

/******************************************************************************
 *  Compilation:  javac DeluxeBouncingBall.java
 *  Execution:    java DeluxeBouncingBall
 *  Dependencies: StdDraw.java StdAudio.java
 *                https://introcs.cs.princeton.edu/java/15inout/BallTap.wav
 *                https://introcs.cs.princeton.edu/java/15inout/BlockHit.wav
 *                https://introcs.cs.princeton.edu/java/15inout/TennisBall.png
 *
 *  Implementation of a 2-d bouncing ball in the box from (-1, -1) to (1, 1).
 *
 *  % java DeluxeBouncingBall
 *
 *  Credits: BallTap.wav and BlockHit.wav are from
 *  https://mixkit.co/free-sound-effects/game/
 *  Free for educational use under the Mixkit Sound Effects Free License.
 *  https://mixkit.co/license/#sfxFree
 *
 ******************************************************************************/

public class DeluxeBouncingBall {
    public static void main(String[] args) {
        double rx = 0.480, ry = 0.860;     // position
        double vx = 0.015, vy = 0.023;     // velocity
        double radius = 0.03;              // a hack since "earth.gif" is in pixels

        // set the scale of the coordinate system
        StdDraw.setXscale(-1.0, 1.0);
        StdDraw.setYscale(-1.0, 1.0);
        StdDraw.enableDoubleBuffering();

        // main animation loop
        while (true) {
            if (Math.abs(rx + vx) + radius > 1.0) {
                vx = -vx;
                StdAudio.playInBackground("BallTap.wav");
            }
            if (Math.abs(ry + vy) + radius > 1.0) {
                vy = -vy;
                StdAudio.playInBackground("BlockHit.wav");
            }
            rx = rx + vx;
            ry = ry + vy;
            StdDraw.clear();
            StdDraw.picture(rx, ry, "TennisBall.png");
            StdDraw.show();
            StdDraw.pause(20);
        }
    }
}