CODEWITHSUNDEEP
javagenericsjava-stream
Andrey Yaskulsky
Andrey Yaskulsky

Reputation: 2516

java 8 collectors for streams with generics

I have a class with long field (primitive type):

class Transfer {
       private long id;
       //gets sets
}

I want to get a List<Long> from Collection<Transfer> which would contain all ids from Collection<Transfer> e.g.

Collection<Transfer> transfers = ..;
List<Long> ids = (List<Long>) transfers.stream().map(f -> f.getId()).collect(Collectors.toList());

The thing which confuses me is this ugly cast: 

(List<Long>) transfers.stream()

Is there any way to avoid it?

Upvotes: 0

Views: 1024

Answers (1)

Tagir Valeev
Tagir Valeev

Reputation: 100139

Assuming that your getId() method return type is long or Long, this cast is absolutely unnecessary. You can write

List<Long> ids = transfers.stream().map(f -> f.getId()).collect(Collectors.toList());

Upvotes: 1

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