DoubleStream flatMap(DoubleFunction 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 :
DoubleStream flatMap(DoubleFunction<? extends DoubleStream> mapper)
Parameters :
- DoubleStream : A sequence of primitive double-valued elements.
- DoubleFunction : A function that accepts an double-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 : DoubleStream flatMap(DoubleFunction mapper) returns a stream by a mapped stream using mapping function.
Example 1 : Using DoubleStream flatMap() to get the cube of elements of DoubleStream.
// Java code for DoubleStream flatMap// (DoubleFunction mapper) to get a stream// consisting of the results of replacing// each element of this stream with the// contents of a mapped streamimport java.util.*;import java.util.stream.DoubleStream;  class GFG {      // Driver code    public static void main(String[] args)    {        // Creating an DoubleStream        DoubleStream stream1 = DoubleStream.of(4.2, 5.3, 6.6, 7.0);          // Using DoubleStream flatMap()        DoubleStream stream2 = stream1.flatMap(num                   -> DoubleStream.of(num * num * num));          // Displaying the resulting DoubleStream        stream2.forEach(System.out::println);    }} |
74.08800000000001 148.87699999999998 287.496 343.0
Example 2 :Using DoubleStream flatMap() to multiply every element of DoubleStream by 0.7
// Java code for DoubleStream flatMap// (DoubleFunction mapper) to get a stream// consisting of the results of replacing// each element of this stream with the// contents of a mapped streamimport java.util.*;import java.util.stream.DoubleStream;  class GFG {      // Driver code    public static void main(String[] args)    {        // Creating an DoubleStream        DoubleStream stream1 = DoubleStream.of(5.2, 6.4, 8.1, 10.0);          // Using DoubleStream flatMap()        DoubleStream stream2 = stream1.flatMap(num                     -> DoubleStream.of(num * 0.7));          // Displaying the resulting IntStream        stream2.forEach(System.out::println);    }} |
3.6399999999999997 4.4799999999999995 5.669999999999999 7.0
