public String[] preferenceNames(){
  Set<String> set=properties.stringPropertyNames();
  return set.toArray(new String[set.size()]);
}

public String [ ] preferenceNames ( ) { Set < String > set = properties . stringPropertyNames ( ) ; return set . toArray ( new String [ set . size ( ) ] ) ; }
returns an enumeration of all preferences known to this store which have current values other than their default value .
