IntStream flatMap(IntFunction mapper) in Java

IntStream flatMap(IntFunction mapper) returns a stream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. This is an intermediate operation. These operations are always lazy. Intermediate operations are invoked on a Stream instance and after they finish their processing, they give a Stream instance as output. Note : Each mapped stream is closed after its contents have been placed into this stream. If a mapped stream is null, an empty stream is used, instead. Syntax :

IntStream flatMap(IntFunction<? extends IntStream> mapper)

Parameters :

1. IntStream : A sequence of primitive int-valued elements.
2. IntFunction : A function that accepts an int-valued argument and produces a result.
3. mapper : A stateless function which is applied to each element and the function returns the new stream.

Return Value : IntStream flatMap(IntFunction mapper) returns a stream by a mapped stream using mapping function. Example 1 : Using IntStream flatMap() to get the cube of elements of IntStream. Output :

64
125
216
343

Example 2 :Using IntStream flatMap() to get the count of set bits in binary representation of elements of IntStream.

Output :

3
1
3
3