@Override
    public boolean equals(Object obj) {
        if (this == obj) {
           return true;
        }
        if (obj == null) {
           return false;
        }
        if (getClass() != obj.getClass()) {
           return false;
        }
        GenericTreeNode<?> other = (GenericTreeNode<?>) obj;
        if (data == null) {
           if (other.data != null) {
              return false;
           }
        } else if (!data.equals(other.data)) {
           return false;
        }
        return true;
    }