Get Array of Property, of Property (nested property) using stream Java 8

Question

Based in this Question...

I have this code:

List<IdDTO> ids = collectionEntityDTO.stream().map(EntityDTO::getId).collect(Collectors.toList());
List<Long> codes = ids.stream().map(IdDTO::getCode).collect(Collectors.toList());
Long[] arrayCodes = codes.toArray(new Long[0]);

How to do this, in this simple manner?

Ousmane D. · Accepted Answer · 2018-12-11 22:27:47Z

4

Your approach is rather inefficient, just chain the methods:

collectionEntityDTO.stream()
        .map(EntityDTO::getId)
        .map(IdDTO::getCode)
        .toArray(Long[]::new);

This approach is better because:

It’s easier to read what’s going on
It’s more efficient as already mentioned as doesn't require eagerly creating new collection objects at each intermediate step.
There's no clutter with garbage variables.
easier to parallelize.

edited Dec 11, 2018 at 22:27

answered Dec 11, 2018 at 22:21

Ousmane D.

56.6k8 gold badges101 silver badges134 bronze badges

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

Collectives™ on Stack Overflow

Get Array of Property, of Property (nested property) using stream Java 8

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