IntStream sum() returns the sum of elements in this stream. This is a special case of a reduction. IntStream 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 :
int sum()
Return Value : The function returns the sum of elements in this stream.
Example 1 :
// Java code for IntStream.sum() to
// find the sum of elements in IntStream
import java.util.*;
import java.util.stream.IntStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating an IntStream
IntStream stream = IntStream.of(2, 4, 6, -2, -4);
// Using IntStream.sum() to find
// sum of elements in IntStream
int sumOfElements = stream.sum();
// Displaying the calculated sum
System.out.println(sumOfElements);
}
}
Output:
6
Example 2 :
// Java code for IntStream.sum() to
// find the sum of elements
// divisible by 3 in given range
import java.util.*;
import java.util.stream.IntStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Using IntStream.sum() to find
// sum of elements divisible by 3
// in given range
int sumOfElements = IntStream.range(2, 10)
.filter(num -> num % 3 == 0)
.sum();
// Displaying the calculated sum
System.out.println(sumOfElements);
}
}
Output:
18