public void updateHashForGroup(final String hash,final String groupName){
  notNull(groupName);
  this.currentHash=hash;
  if (isChangedHash()) {
    LOG.debug("Group {} has changed",groupName);
    groups.clear();
  }
}

public void updateHashForGroup ( final String hash , final String groupName ) { notNull ( groupName ) ; this . currentHash = hash ; if ( isChangedHash ( ) ) { LOG . debug ( "Group {} has changed" , groupName ) ; groups . clear ( ) ; } }
updates the hash associated with the resource for a give groupname .
