java 8 collect List

Question

I am collecting String in List using Java 8. But, this is giving me compile error that

incompatible types: inference variable T has incompatible bounds equality constraints: String lower bounds: Object

final List<ProjectLevel> levels = projectLevelFacade
                    .findUUIDByNameorNumber(freeText, businessAccountId);
final List<String> uuids = levels
                    .stream()
                    .map((level) -> level.getProjectLevelsUUIDs()) // this return List<String>
                    .flatMap(Collection::stream)
                    .collect(Collectors.toList());

can any one have idea how to achieve this using Java 8?

Is there any type of casting or something for this?

I have also taken reference from here.

Is `ProjectLevel` a generic? Should it be `ProjectLevel>` otherwise `getProjectLevelsUUIDs()` won't be generic either. — Peter Lawrey, Dec 30 '16 at 10:57
@PavneetSingh it shouldn't work as error droves me somewhere else. still let me try — Hiren, Dec 30 '16 at 10:59
I think you’d better provide a [Minimal, Complete, and Verifiable example](http://stackoverflow.com/help/mcve). — Ole V.V., Dec 30 '16 at 11:02
When you treat a class with generic types as a raw type, all it's methods and return values become raw types even if they didn't use the generic parameter. — Peter Lawrey, Dec 30 '16 at 14:07

score 4 · Accepted Answer · answered Dec 30 '16 at 11:02

4

ProjectLevel is a generic class - when you write List<ProjectLevel> you are using a raw type and the type inference system does not work any longer.

Try:

final List<ProjectLevel<?>> levels = projectLevelFacade
                .findUUIDByNameorNumber(freeText, businessAccountId);

and it should compile as expected.

answered Dec 30 '16 at 11:02

assylias

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it worked! but the problem arising now is from namedQuery it returns no generic. Means it returns `List`. so not able to return it in `List>` – Hiren Dec 30 '16 at 11:08
2

@Hiru then you need to change that method too. – assylias Dec 30 '16 at 11:12
yes i tried this but in named query i am not able to `getResultList()` in `List>` – Hiren Dec 30 '16 at 11:17
1

I think i would have to ask separate question for this – Hiren Dec 30 '16 at 11:20
2

@Hiru probably easier indeed – assylias Dec 30 '16 at 11:21
posted another thread. If you have any idea please suggest me – Hiren Dec 30 '16 at 11:29
2

I had a look but I don't use JPA so not sure how to fix your problem. – assylias Dec 30 '16 at 11:36

java 8 collect List

1 Answers1