Java 8 Streams - LongStream.flatMap Examples

[Last Updated: Nov 8, 2025]

Interface:

java.util.stream.LongStream

Method:

LongStream flatMap(LongFunction<? extends LongStream> mapper)

This intermediate operation 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. 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.

Examples

package com.logicbig.example.longstream;

import java.util.Arrays;
import java.util.stream.LongStream;

public class FlatMapExample {

    public static void main(String... args) {
        long[] ints = {10, 20, 30, 40};
        LongStream stream = Arrays.stream(ints);
        LongStream stream2 = stream.flatMap(FlatMapExample::multipleOf);
        stream2.forEach(System.out::println);
    }

    private static LongStream multipleOf(long l) {
        return LongStream.iterate(l, j -> j + l)
                         .limit(5);
    }
}

Output

Java 8 Streams - LongStream.flatMap Examples

Interface:

Method:

Examples

Output

See Also