public boolean equals(Object obj) {
    if (obj == null || !(obj instanceof Param))
      return false;
    Param other = (Param)obj;
    if (this.type != other.type)
      return false;
    if (this.entity != other.entity)
      return false;
    if (this.value != null && !this.value.equals(other.value))
      return false;
    if (this.group != null && !this.group.equals(other.group))
      return false;
    return true;
  }