Java 8 primitive stream to collection mapping methods

Question

Is there any significant difference (in performance or best practices) between those two stream creation methods?

int[] arr2 = {1,2,3,4,5,6};

Arrays.stream(         


        

Answer 1

For both performance and best practices, we should choose boxed() over mapToObj((in) -> new Integer(in)).

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Performance:

See below boxed() source code (in the abstract class IntPipeline which implements IntStream, in the package java.util.stream ):

@Override
    public final Stream boxed() {
        return mapToObj(Integer::valueOf);
    }

So it is calling mapToObj() with Integer::valueOf. Note that by reusing cached values,Integer::valueOf is more efficient than new Integer() , so we should choose boxed().

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Best practice:

Besides the performance difference, with boxed() we write less, and it is easier to read.