Java 8 convert List to Lookup Map

Question

I have a list of Station, in each Station there is a list of radios. I need to create a lookup Map of radio to Station. I know how to use Java 8 stream forEach to do it:

Answer 1

How about:

radioToStationMap = StreamEx.of(stationList)
        .flatMapToEntry(s -> StreamEx.of(s.getRadioList()).mapToEntry(r -> s).toMap())
        .toMap();

By StreamEx