@ Override public Set < Integer > keySet ( ) { // use a linkedhashset so values come out in order Set < Integer > ret = new LinkedHashSet <> ( ) ; for ( Tuple2 < String , Integer > t : wrapped . keySet ( ) ) { ret . add ( t . b ) ; } // Don't let the user modify the set as it won't do what they expect (change the map) return Collections . unmodifiableSet ( ret ) ; }
We currently just expose them as immutable sets in RAM since all of the modification operations are optional .