Grouping by in Java 8 stream to custom class rather than the origin class

Question

I have a class A which has some fields.

Class A{
 String type;
 String x;
 String y;
}

Class B{
    String x;
    String y;

}

Let's say we have a list List<A>. By using Collectors.groupingBy() , is it possible to get output Map<String,List<B>> instead Map<String,List<A>> ? where key in the Map is type field in Class A.

Collectors.groupingBy(..., Collectors.mapping(....))

Eugene
– Eugene

2019-05-13 10:35:29 +00:00
Commented May 13, 2019 at 10:35 — Eugene
– Eugene, Commented May 13, 2019 at 10:35

Eran · Accepted Answer · 2019-05-13 10:37:21Z

1

Of course - just chain a mapping() collector to the groupingBy() collector.

Map<String,List<B>> map =
    listA.stream()
         .collect(Collectors.groupingBy(A::getType,
                                        Collectors.mapping(a->new B(a.getX(),a.getY()),
                                                           Collectors.toList())));

answered May 13, 2019 at 10:37

Eran

395k57 gold badges726 silver badges793 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Grouping by in Java 8 stream to custom class rather than the origin class

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related