question: public boolean add ( K key , V item ) { Set < V > values = map . get ( key ) ; if ( values == null ) { values = ( sorted ? new TreeSet < V > ( ) : new HashSet < V > ( ) ) ; map . put ( key , values ) ; } if ( item == null ) return false ; return values . add ( item ) ; }
target:  Adds item to the set of values associated with the key (null items are not added)