In this blog, we are going to learn about finding the sum of all the numbers in a list using in Java 8.

Stream java.util.Collection.stream()

Returns a sequential Stream with this collection as its source.

java.util.stream.Stream.mapToInt(ToIntFunction<? super Integer> mapper)

Returns an IntStream consisting of the results of applying the given function to the elements of this stream.

java.util.stream.IntStream.sum()

Returns the sum of elements in this stream. This is a special case of a reduction and is equivalent to:

return reduce(0, Integer::sum);

This is a terminal operation.
Returns:
the sum of elements in this stream Example:

import java.util.Arrays;
import java.util.List;

public class BehindJava {

	public static void main(String[] args) {

		List<Integer> list = Arrays.asList(77, 42, 35, 12, 101, 5);
		int sum = list.stream().mapToInt(n -> n).sum();
		System.out.println("Sum: " + sum);
	}
}

Output:

Sum: 272