public boolean testCollision(Sprite testSprite) {
// Check for collision with
// another sprite
if (testSprite != this) {
return spaceOccupied.intersects(testSprite.getSpaceOccupied());
} // end if
return false;
} // end testCollision
public void update() {
Sprite sprite;
// Iterate through sprite list
for (int cnt = 0; cnt < size(); cnt++) {
sprite = (Sprite) elementAt(cnt);
// Update a sprite's position
sprite.updatePosition();
// Test for collision. Positive
// result indicates a collision
int hitIndex = testForCollision(sprite);
if (hitIndex >= 0) {
// a collision has occurred
bounceOffSprite(cnt, hitIndex);
} // end if
} // end for loop
} // end update
private void bounceOffSprite(int oneHitIndex, int otherHitIndex) {
// Swap motion vectors for
// bounce algorithm
Sprite oneSprite = (Sprite) elementAt(oneHitIndex);
Sprite otherSprite = (Sprite) elementAt(otherHitIndex);
Point swap = oneSprite.getMotionVector();
oneSprite.setMotionVector(otherSprite.getMotionVector());
otherSprite.setMotionVector(swap);
} // end bounceOffSprite()
private int testForCollision(Sprite testSprite) {
// Check for collision with other
// sprites
Sprite sprite;
for (int cnt = 0; cnt < size(); cnt++) {
sprite = (Sprite) elementAt(cnt);
if (sprite == testSprite)
// don't check self
continue;
// Invoke testCollision method
// of Sprite class to perform
// the actual test.
if (testSprite.testCollision(sprite))
// Return index of colliding
// sprite
return cnt;
} // end for loop
return -1; // No collision detected
} // end testForCollision()