code: public CharacterSet getInverse() {
  		CharacterSet n = new CharacterSet();
  		n.forbiddenCharacters = characters;
  		n.characters = forbiddenCharacters;
  		return n;
  	}
docs: Returns a CharacterSet instance whose allowed and forbidden characters are exactly inverse to
  this instance.
  
  @return a CharacterSet instance whose allowed and forbidden characters are exactly inverse to
  this instance