DoubleStream sum() returns the sum of elements in this stream. This is a special case of a reduction. DoubleStream sum() is a terminal operation i.e, it may traverse the stream to produce a result or a side-effect.
Note : A reduction operation (also called a fold) takes a sequence of input elements and combines them into a single summary result by repeated application of a combining operation, such as finding the sum or maximum of a set of numbers.
Syntax :
double sum()
Return Value : The function returns the sum of elements in this stream.
Note :
- If any stream element is a NaN or the sum is at any point a NaN then the sum will be NaN.
- Elements sorted by increasing absolute magnitude tend to yield more accurate result.
Example 1 :
// Java code for DoubleStream.sum() to// find the sum of elements in DoubleStreamimport java.util.*;import java.util.stream.DoubleStream;  class GFG {      // Driver code    public static void main(String[] args)    {        // Creating an DoubleStream        DoubleStream stream = DoubleStream.of(2.2, 4.3, 6.4,                                              -2.5, -4.6);          // Using DoubleStream.sum() to find        // sum of elements in DoubleStream        double sumOfElements = stream.sum();          // Displaying the calculated sum        System.out.println(sumOfElements);    }} |
Output:
5.800000000000001
Example 2 :
// Java code for DoubleStream.sum() to// find the sum of elements// greater than 2.5import java.util.*;import java.util.stream.DoubleStream;  class GFG {      // Driver code    public static void main(String[] args)    {        // Creating an DoubleStream        // Using DoubleStream.sum() to find        // sum of elements greater than 2.5        double sumOfElements = DoubleStream.of(2.2, 4.2, 6.4,                                               -2.5, -4.5)                                   .filter(num -> num > 2.5)                                   .sum();          // Displaying the calculated sum        System.out.println(sumOfElements);    }} |
Output:
10.600000000000001
