public Set<String> keySet(){
  HashSet<String> set=new HashSet<String>();
  Iterator<String> keys=keys();
  while (keys.hasNext()) {
    set.add(keys.next());
  }
  return set;
}

public Set < String > keySet ( ) { HashSet < String > set = new HashSet < String > ( ) ; Iterator < String > keys = keys ( ) ; while ( keys . hasNext ( ) ) { set . add ( keys . next ( ) ) ; } return set ; }
returns a set containing all keys on this object . if possible , use the keys iterator instead for improved performance .
