BulletCollision.java

for (int p=0;p<entities.size();p++) {
	for (int s=p+1;s<entities.size();s++) {
		Entity me = (Entity) entities.get(p);
		Entity him = (Entity) entities.get(s);
			
		if (me.collidesWith(him)) {
			me.collidedWith(him);
			him.collidedWith(me);
		}
	}
}