Java 8 Streams - DoubleStream.flatMap Examples

Java 8 Streams Java Java API 

Interface:

java.util.stream.DoubleStream

Method:

DoubleStream flatMap(DoubleFunction<? extends DoubleStream> 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.doublestream;

import java.util.Arrays;
import java.util.stream.DoubleStream;

public class FlatMapExample {

    public static void main(String... args) {
        DoubleStream ds = DoubleStream.of(1.1, 2.4, 3.2, 4.3);
        double[] doubles = ds.flatMap(value ->
                DoubleStream.of(value * 0.5, value))
                             .toArray();
        System.out.println(Arrays.toString(doubles));
    }
}

Output

[0.55, 1.1, 1.2, 2.4, 1.6, 3.2, 2.15, 4.3]