Grouping objects by two fields using Java 8

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I have a problem grouping two values with Java 8.

My main problem is about grouping two fields, I group correctly one field called getNameOfCountryOrRegion() but now I am interested in groupingBy another field that is called leagueDTO as well.

Map<String, List<FullCalendarDTO>> result =                .collect(Collectors.groupingBy(                              FullCalendarDTO::getNameOfCountryOrRegion)); 

And the following class :

public class FullCalendarDTO  {     private long id;     private TeamDTO localTeam;     private TeamDTO visitorTeam;     private LocationDTO location;        private String leagueDTO;            private String timeStamp;     private String nameOfCountryOrRegion; } 

The result will be grouped by nameOfCountryOrRegion and leagueDTO.


Passing a downstream collector to groupingBy will do the trick:               .collect(groupingBy(FullCalendarDTO::getNameOfCountryOrRegion,                        groupingBy(FullCalendarDTO::getLeagueDTO))); 

The code snippet above will group your FullCalendarDTO objects by nameOfCountryOrRegion then each group will be grouped by leagueDTO.

So the returned collection will look like Map<String, Map<String, List<FullCalendarDTO>>>.


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