code: public boolean isRepeated(final String _plainPassword)
      {
          boolean ret = false;
          for (int i = 1; i < this.threshold + 1; i++) {
              ret = check(_plainPassword, i);
              if (ret) {
                  break;
              }
          }
          return ret;
      }
docs: Is the given plain password repeated. It is checked against the existing
  previous passwords.
  
  @param _plainPassword plain text password
  @return true if repeated, else false