Stream.reduce() in Java with examples

// Implementation of reduce method
// to get the longest String
import java.util.*;

class GFG {
    public static void main(String[] args) {
        // Creating a list of Strings
        List<String> words = Arrays.asList("GFG", "Geeks", "for", "GeeksQuiz", "GeeksforGeeks");

        // Using reduce to find the longest string in the list
        Optional<String> longestString = words.stream()
            .reduce((word1, word2) -> word1.length() > word2.length() ? word1 : word2);

        // Displaying the longest String
        longestString.ifPresent(System.out::println); 
    }
}

// Implementation of reduce method
// to get the combined String
import java.util.*;

class GFG {
    public static void main(String[] args) {
        // String array to combine
        String[] array = { "Geeks", "for", "Geeks" };

        // Using reduce to concatenate strings with a hyphen
        Optional<String> combinedString = Arrays.stream(array)
            .reduce((str1, str2) -> str1 + "-" + str2);

        // Displaying the combined String
        combinedString.ifPresent(System.out::println); 
    }
}

// Implementation of reduce method
// to get the sum of all elements
import java.util.*;

class GFG {
    public static void main(String[] args) {
        // Creating list of integers
        List<Integer> numbers = Arrays.asList(-2, 0, 4, 6, 8);

        // Using reduce to find the sum of all elements
        int sum = numbers.stream()
            .reduce(0, (element1, element2) -> element1 + element2);

        // Displaying the sum of all elements
        System.out.println("The sum of all elements is " + sum); 
    }
}

// Implementation of reduce method
// to get the product of all numbers
// in given range.
import java.util.*;
import java.util.stream.IntStream;

class GFG {
    public static void main(String[] args) {
        // Calculating the product of all numbers in the range [2, 8)
        int product = IntStream.range(2, 8)
            .reduce((num1, num2) -> num1 * num2)
            .orElse(-1); // Provides -1 if the stream is empty

        // Displaying the product
        System.out.println("The product is : " + product); 
    }
}