public boolean deleteElementField(ElementField element) {
        if (element instanceof Ball) {
            return _balls.remove((Ball) element);
        } else if (element instanceof DestructibleBrick) {
            return _dBricks.remove((DestructibleBrick) element);
        } else if (element instanceof BoundaryField) {
            return _bondarysField.remove((BoundaryField) element);
        } else if (element instanceof Swarm) {
            return _swarms.remove((Swarm) element);
        } else if (element instanceof IndestructibleBrick) {
            return _iBricks.remove((IndestructibleBrick) element);
        } else if (element instanceof Racket) {
            _racket = null;
            return true;
        }
        return false;
    }