java 8 stream option

In Java 8 and later, the java.util.stream package provides the Stream interface, which represents a sequence of elements that can be processed sequentially or in parallel.

A Stream can be created from a variety of sources, such as a Collection, an array, a generator function, or an I/O channel.

Once a Stream is created, it can be transformed and processed using a variety of intermediate and terminal operations.

Intermediate operations are operations that return a new Stream, such as filter, map, or sorted, and allow you to transform the elements of the Stream in various ways.

Terminal operations are operations that return a result or perform an action on the elements of the Stream, such as collect, count, or forEach, and allow you to consume the elements of the Stream.

Here is an example of how you can use the Stream interface to filter a List of integers and calculate the sum of the even numbers:

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

public class MyClass {
    public static void main(String[] args) {
        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

        int sum = numbers.stream()
            .filter(n -> n % 2 == 0) // keep only even numbers
            .mapToInt(n -> n) // convert to IntStream
            .sum(); // calculate the sum

        System.out.println(sum); // Outputs 30
    }
}

In this example, the numbersList contains the integers from 1 to 10.

The filter intermediate operation keeps only the even numbers, the mapToInt intermediate operation converts the Stream of integers to an IntStream, and the sum terminal operation calculates the sum of the even numbers.

The result of the stream processing is printed to the console.