Not necessarily a bump, but it's worth this post.

I have found another solution on Google by chance, and I decided to help others who are also looking for collision responses by linking directly and save time Googling for one.

The link is here.

The alternate solution (Author: eBusiness):

public void handleCollisions(){
	double xDist, yDist;
	for(int i = 0; i < balls.size(); i++){
		Ball A = balls.get(i);
		for(int j = i+1; j < balls.size(); j++){
			Ball B = balls.get(j);
			xDist = A.getCenterX() - B.getCenterX();
			yDist = A.getCenterY() - B.getCenterY();
			double distSquared = xDist*xDist + yDist*yDist;
			//Check the squared distances instead of the the distances, same result, but avoids a square root.
			if(distSquared <= (A.radius + B.radius)*(A.radius + B.radius)){
				double xVelocity = B.xVel - A.xVel;
				double yVelocity = B.yVel - A.yVel;
				double dotProduct = xDist*xVelocity + yDist*yVelocity;
				//Neat vector maths, used for checking if the objects moves towards one another.
				if(dotProduct > 0){
					double collisionScale = dotProduct / distSquared;
					double xCollision = xDist * collisionScale;
					double yCollision = yDist * collisionScale;
					//The Collision vector is the speed difference projected on the Dist vector,
					//thus it is the component of the speed difference needed for the collision.
					double combinedMass = A.mass + B.mass;
					double collisionWeightA = 2 * B.mass / combinedMass;
					double collisionWeightB = 2 * A.mass / combinedMass;
					A.xVel += collisionWeightA * xCollision;
					A.yVel += collisionWeightA * yCollision;
					B.xVel -= collisionWeightB * xCollision;
					B.yVel -= collisionWeightB * yCollision;
				}
			}
		}
	}
}

Not necessarily a bump, but it's worth this post.

I have found another solution on Google by chance, and I decided to help others who are also looking for collision responses by linking directly and save time Googling for one.

The link is here.

The alternate solution:

public void handleCollisions(){
    double xDist, yDist;
    for(int i = 0; i < balls.size(); i++){
	    Ball A = balls.get(i);
	    for(int j = i+1; j < balls.size(); j++){
		    Ball B = balls.get(j);
		    xDist = A.getCenterX() - B.getCenterX();
		    yDist = A.getCenterY() - B.getCenterY();
		    double distSquared = xDist*xDist + yDist*yDist;
		    //Check the squared distances instead of the the distances, same result, but avoids a square root.
		    if(distSquared <= (A.radius + B.radius)*(A.radius + B.radius)){
			    double xVelocity = B.xVel - A.xVel;
			    double yVelocity = B.yVel - A.yVel;
			    double dotProduct = xDist*xVelocity + yDist*yVelocity;
			    //Neat vector maths, used for checking if the objects moves towards one another.
			    if(dotProduct > 0){
				    double collisionScale = dotProduct / distSquared;
				    double xCollision = xDist * collisionScale;
				    double yCollision = yDist * collisionScale;
				    //The Collision vector is the speed difference projected on the Dist vector,
				    //thus it is the component of the speed difference needed for the collision.
				    double combinedMass = A.mass + B.mass;
				    double collisionWeightA = 2 * B.mass / combinedMass;
				    double collisionWeightB = 2 * A.mass / combinedMass;
				    A.xVel += collisionWeightA * xCollision;
				    A.yVel += collisionWeightA * yCollision;
				    B.xVel -= collisionWeightB * xCollision;
				    B.yVel -= collisionWeightB * yCollision;
			    }
		    }
	    }
    }
}