java/examples/Topics/Motion/Bounce/applet/Bounce.java

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+import processing.core.*; 
+
+import java.applet.*; 
+import java.awt.*; 
+import java.awt.image.*; 
+import java.awt.event.*; 
+import java.io.*; 
+import java.net.*; 
+import java.text.*; 
+import java.util.*; 
+import java.util.zip.*; 
+import java.util.regex.*; 
+
+public class Bounce extends PApplet {
+
+/**
+ * Bounce. 
+ * 
+ * When the shape hits the edge of the window, it reverses its direction. 
+ */
+ 
+int size = 60;       // Width of the shape
+float xpos, ypos;    // Starting position of shape    
+
+float xspeed = 2.8f;  // Speed of the shape
+float yspeed = 2.2f;  // Speed of the shape
+
+int xdirection = 1;  // Left or Right
+int ydirection = 1;  // Top to Bottom
+
+
+public void setup() 
+{
+  size(640, 200);
+  noStroke();
+  frameRate(30);
+  smooth();
+  // Set the starting position of the shape
+  xpos = width/2;
+  ypos = height/2;
+}
+
+public void draw() 
+{
+  background(102);
+  
+  // Update the position of the shape
+  xpos = xpos + ( xspeed * xdirection );
+  ypos = ypos + ( yspeed * ydirection );
+  
+  // Test to see if the shape exceeds the boundaries of the screen
+  // If it does, reverse its direction by multiplying by -1
+  if (xpos > width-size || xpos < 0) {
+    xdirection *= -1;
+  }
+  if (ypos > height-size || ypos < 0) {
+    ydirection *= -1;
+  }
+
+  // Draw the shape
+  ellipse(xpos+size/2, ypos+size/2, size, size);
+}
+
+  static public void main(String args[]) {
+    PApplet.main(new String[] { "Bounce" });
+  }
+}