DoubleStream parallel() in Java

DoubleStream parallel() is a method in java.util.stream.DoubleStream. This method returns a parallel DoubleStream, i.e, it may return itself, either because the stream was already present, or because the underlying stream state was modified to be parallel.

DoubleStream parallel() 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.

Syntax :

DoubleStream parallel()

Where, DoubleStream is a sequence of primitive 
double-valued elements and the function 
returns a parallel DoubleStream.

Example 1 :

// Java program to demonstrate working of
// DoubleStream parallel() on a given range
import java.util.*;
import java.util.stream.DoubleStream;

class GFG {

    // Driver code
    public static void main(String[] args)
    {
        // Creating a stream of doubles
        DoubleStream stream =
              DoubleStream.of(5.2, 12.6, 4.5, 7.8);

        System.out.println("The corresponding "
                           + "parallel DoubleStream is :");
        stream.parallel().forEach(System.out::println);
    }
}

Output :

The corresponding parallel DoubleStream is :
4.5
7.8
12.6
5.2

Example 2 :

// Printing sequential stream for the
// same input as above example 1.
import java.util.*;
import java.util.stream.DoubleStream;

class GFG {

    // Driver code
    public static void main(String[] args)
    {
        // Creating a stream of doubles
        DoubleStream stream =
                 DoubleStream.of(5.2, 12.6, 4.5, 7.8);

        System.out.println("The corresponding "
                           + "sequential DoubleStream is :");
        stream.sequential().forEach(System.out::println);
    }
}

Output :

The corresponding sequential DoubleStream is :
5.2
12.6
4.5
7.8

Example 3 :

// Java program to show sorted output
// of parallel stream.
import java.util.*;
import java.util.stream.DoubleStream;

class GFG {

    // Driver code
    public static void main(String[] args)
    {
        // Creating a stream of doubles
        DoubleStream stream =
                DoubleStream.of(2.3, 3.0, 4.5, 6.6);

        System.out.println("The sorted parallel"
                           + " DoubleStream is :");
        stream.parallel().sorted().forEach(System.out::println);
    }
}

Output :

The sorted parallel DoubleStream is :
4.5
6.6
2.3
3.0