public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof GridArrangement)) {
            return false;   
        }
        GridArrangement that = (GridArrangement) obj;
        if (this.columns != that.columns) {
            return false;   
        }
        if (this.rows != that.rows) {
            return false;   
        }
        return true;