How to sum a list of integers with java streams?

You can use the reduce() operation in the Java Streams API to sum the elements of a list of integers. The reduce() operation combines all the elements of the stream into a single result, using a specified accumulator function.

Here's an example of how you can use reduce() to sum the elements of a list of integers:

List<Integer> list = Arrays.asList(1, 2, 3, 4, 5);

int sum = list.stream()
              .reduce(0, (a, b) -> a + b);

System.out.println(sum);  // prints 15

In this example, the accumulator function is a lambda expression that takes two arguments, a and b, and returns the sum of a and b. The initial value of the accumulator is 0.

You can also use the sum() method of the IntStream class to sum the elements of a list of integers. Here's an example of how you can use IntStream.sum() to sum the elements of a list of integers:

List<Integer> list = Arrays.asList(1, 2, 3, 4, 5);

int sum = list.stream()
              .mapToInt(Integer::intValue)
              .sum();

System.out.println(sum);  // prints 15

I hope this helps! Let me know if you have any questions.