IntStream flatMap(IntFunction mapper) in Java

Last Updated : 06 Dec, 2018

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 :

IntStream : A sequence of primitive int-valued elements.
IntFunction : A function that accepts an int-valued argument and produces a result.
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.

Java

// Java code for IntStream flatMap
// (IntFunction mapper) to get a stream
// consisting of the results of replacing
// each element of this stream with the
// contents of a mapped stream
import java.util.*;
import java.util.stream.IntStream;

class GFG {

    // Driver code
    public static void main(String[] args)
    {
        // Creating an IntStream
        IntStream stream1 = IntStream.of(4, 5, 6, 7);

        // Using IntStream flatMap()
        IntStream stream2 = stream1.flatMap(num
                  -> IntStream.of(num * num * num));

        // Displaying the resulting IntStream
        stream2.forEach(System.out::println);
    }
}

Output :

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

Java

// Java code for IntStream flatMap
// (IntFunction mapper) to get a stream
// consisting of the results of replacing
// each element of this stream with the
// contents of a mapped stream
import java.util.*;
import java.util.stream.IntStream;

class GFG {

    // Driver code
    public static void main(String[] args)
    {
        // Creating an IntStream
        IntStream stream1 = IntStream.of(49, 64, 81, 100);

        // Using IntStream flatMap()
        IntStream stream2 = stream1.flatMap(num
               -> IntStream.of(Integer.bitCount(num)));

        // Displaying the resulting IntStream
        stream2.forEach(System.out::println);
    }
}

Output :

IntFunction Interface in Java with Examples

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IntStream flatMap(IntFunction mapper) in Java

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