code: boolean putIfMissing(Key key, V value){
  
  		if(containsKey(key)){
  			return false;
  		}
  
  		put(key, value);
  
  		return true;
  	}
docs: @return <code>true</code> If the {@link #keySet() key set} of the map was modified, <code>false</code> otherwise.
  
  @see #removeIfPresent(Key)