@Override
        public boolean equals(Object obj) {
            if (obj == null) {
                return false;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            final WindowingCommand other = (WindowingCommand) obj;
            if (this.lower != other.lower) {
                return false;
            }
            return this.higher == other.higher;
        }