Question

is it possible for the following element to return multiple items in one call ( i.e. two GRects)

    private GObject getColidingObject(){
    if(getElementAt(ball.getX(), ball.getY()) != null){
        return getElementAt(ball.getX(), ball.getY());
    }else if(getElementAt(ball.getX() + BALL_RADIUS *2, ball.getY()) != null){
        return getElementAt(ball.getX() + BALL_RADIUS *2, ball.getY());
    }else if(getElementAt(ball.getX(), ball.getY() + BALL_RADIUS *2) != null){
        return getElementAt(ball.getX(), ball.getY() + BALL_RADIUS *2);
    }else if(getElementAt(ball.getX() + BALL_RADIUS *2, ball.getY() + BALL_RADIUS *2) != null){
        return getElementAt(ball.getX() + BALL_RADIUS *2, ball.getY() + BALL_RADIUS *2);
    }else{
        return null;
    }
}

Answer 1

You can only return one value, but you could make that value an array. For example:

private GObject[] getCollidingObjects() {
    GObject[] ret = new GObject[2];

    ret[0] = ...;
    ret[1] = ...;
    return ret;
}

Btw, when you start reusing the same expression multiple times in the same method, you should think about introducing a local variable for clarity. For example, consider this instead of your original code:

private GObject getCollidingObject(){
    int x = ball.getX();
    int y = ball.getY();
    if (getElementAt(x, y) != null) {
        return getElementAt(x, y);
    }
    if (getElementAt(x + BALL_RADIUS * 2, y) != null) {
        return getElementAt(x + BALL_RADIUS * 2, y);
    }
    if (getElementAt(x, y + BALL_RADIUS * 2) != null) {
        return getElementAt(x, y + BALL_RADIUS * 2);
    }
    if (getElementAt(x + BALL_RADIUS * 2, y + BALL_RADIUS * 2) != null) {
        return getElementAt(x + BALL_RADIUS * 2, y + BALL_RADIUS * 2);
    }
    return null;
}

(You could do the same for x + BALL_RADIUS * 2 and y + BALL_RADIUS * 2 as well.)

You might also consider something like this:

private GObject getCollidingObject(){
    int x = ball.getX();
    int y = ball.getY();
    return getFirstNonNull(getElementAt(x, y),
        getElementAt(x + BALL_RADIUS * 2, y),
        getElementAt(x, y + BALL_RADIUS * 2),
        getElementAt(x + BALL_RADIUS * 2, y + BALL_RADIUS * 2));
}

private static getFirstNonNull(GObject... objects) {
    for (GObject x : objects) {
        if (x != null) {
            return x;
        }
    }
    return null;
}

(In C# there’s a nicer way of doing this with the null coalescing operator, but never mind…)