Example: Sum of Array Elements using Java 8 Stream API (reduce()) in Java

// Sum of Array Elements using Java 8 Stream API (reduce())
import java.util.Arrays; // Required for Arrays.stream()
import java.util.OptionalInt; // For the result of reduce()

// Main class containing the entry point of the program
public class Main {
    public static void main(String[] args) {
        // Step 1: Define the array of integers
        int[] numbers = {10, 20, 30, 40, 50};

        // Step 2: Convert the array to an IntStream and apply the reduce operation
        // reduce(identity, accumulator)
        // identity: The initial value of the reduction, and the default result if the stream is empty.
        // accumulator: A BiFunction that takes two arguments and returns one.
        int sum = Arrays.stream(numbers).reduce(0, (a, b) -> a + b);

        // Step 3: Print the calculated sum
        System.out.println("Sum of array elements (Stream API reduce()): " + sum);

        // Alternative with OptionalInt for empty streams (if no identity is provided)
        OptionalInt optionalSum = Arrays.stream(numbers).reduce(Integer::sum);
        if (optionalSum.isPresent()) {
            System.out.println("Sum with reduce (OptionalInt): " + optionalSum.getAsInt());
        } else {
            System.out.println("Stream was empty (OptionalInt).");
        }
    }
}