Collectors.mapToInt

Collectors.mapToInt is a static method in the Java Stream API that is used to perform a reduction operation on a stream of elements and collect the result as an IntStream. It allows you to convert a stream of objects to an IntStream by applying a mapping function to each element and then summing or reducing the resulting values.

Here's an example usage of Collectors.mapToInt:

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        List<String> numbers = Arrays.asList("1", "2", "3", "4", "5");

        int sum = numbers.stream()
                .mapToInt(Integer::parseInt)
                .sum();

        System.out.println("Sum: " + sum);
    }
}

In this example, we have a list of strings representing numbers. We use `numbers.stream()` to create a stream of these strings. Then, we use `mapToInt(Integer::parseInt)` to convert each string to an integer value using the `parseInt` method from the `Integer` class. Finally, we call `sum()` to calculate the sum of all the integers in the stream.

The output will be:

Sum: 15

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