001 // Faller.java
002 // Created: Wednesday, September 22, 1999 10:02:24 PM
003
004 package ballworld;
005
006 import cs101.lang.Animate;
007
008 /**
009 * A Ball that falls and bounces.
010 * @author (original author unknown)
011 * @author Patrick G. Heck gus.heck@olin.edu
012 * @version $Id: Faller.java,v 1.4 2004/02/09 21:06:45 gus Exp $
013 */
014 public class Faller implements Ball, Animate
015 {
016 // fields:
017 double x=0; // current x position
018 double y=0; // current y position
019 double dx=0; // current x velocity
020 double dy=0; // current y velocity
021
022 World world;
023
024 /** Create a faller that starts at the top, center of the screen
025 * @param w The world we are being creted in
026 */
027 public Faller(World w) {
028 this.world = w;
029 this.x = 0;
030 this.y = world.getMaxY()-1;
031 }
032
033 // contract methods from Ball
034
035 // inherits doc from Ball
036 public double getX() {
037 return x;
038 }
039
040 // inherits doc from Ball
041 public double getY() {
042 return y;
043 }
044
045 // inherits doc from Ball
046 public double getRadius() {
047 return 5;
048 }
049
050 // inherits doc from Ball
051 public void setWorld(World theWorld) {
052 this.world= theWorld;
053 this.dx=(Math.random()-0.5)*2;
054 this.dy= -Math.random()*2;
055 }
056
057 // inherits doc from Ball
058 public void userClicked(double atX, double atY) {
059 }
060
061 // inherits doc from Ball
062 public void userTyped(char key) {
063 }
064
065 /**
066 * Make sure that we stay inside the ball world.
067 */
068 private void checkBounds() {
069 if (x<=world.getMinX() || x>=world.getMaxX()) {
070 dx= -dx;
071 }
072 if (y<world.getMinY() || y>=world.getMaxY()) {
073 dy= -dy;
074 } else {
075 dy= dy - 0.01;
076 }
077 }
078
079 // inherits doc from Animate
080 public void act() {
081 this.checkBounds();
082 x= x+dx;
083 y= y+dy;
084 Ball other= world.getClosestBall(this);
085 if (other != null) {
086 double dx= other.getX()-this.getX();
087 double dy= other.getY()-this.getY();
088 if (dx*dx+dy*dy < 1) {
089 world.removeBall(this);
090 world.removeBall(other);
091 }
092 }
093 }
094 }