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# LongStream sum() in Java

LongStream sum() returns the sum of elements in this stream. This is a special case of a reduction. LongStream 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 :

`long sum()`

Return Value : The function returns the sum of elements in this stream.

Example 1 :

## Java

 `// Java code for LongStream.sum() to``// find the sum of elements in LongStream``import` `java.util.*;``import` `java.util.stream.LongStream;` `class` `GFG {` `    ``// Driver code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``// Creating an LongStream``        ``LongStream stream = LongStream.of(2L, 4L, 6L, -2L, -4L);` `        ``// Using LongStream.sum() to find``        ``// sum of elements in LongStream``        ``long` `sumOfElements = stream.sum();` `        ``// Displaying the calculated sum``        ``System.out.println(sumOfElements);``    ``}``}`

Output:

`6`

Example 2 :

## Java

 `// Java code for LongStream.sum() to``// find the sum of elements``// divisible by 3 in given range``import` `java.util.*;``import` `java.util.stream.LongStream;` `class` `GFG {` `    ``// Driver code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``// Using LongStream.sum() to find``        ``// sum of elements divisible by 3``        ``// in given range``        ``long` `sumOfElements = LongStream.range(2L, 10L)``                                 ``.filter(num -> num % ``3` `== ``0``)``                                 ``.sum();` `        ``// Displaying the calculated sum``        ``System.out.println(sumOfElements);``    ``}``}`

Output:

`18`

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