import java.util.Arrays;
import java.util.List;
public class JavaStreamReducer {
public static void main(String[] args) {
// Reduce Array to String.
String[] people = { "Jack", "Steve", "Alice" };
Arrays.stream(people).reduce((x, y) -> x + " | " + y).ifPresent(s -> System.out.println(s));
// Reduce List to String.
System.out.println("\n");
List<String> peoplelist = Arrays.asList(people);
peoplelist.stream().reduce((x, y) -> x + "," + y).ifPresent(s -> System.out.println(s));
System.out.println("\n");
// function programming with Stream
String greeting = greet(peoplelist);
System.out.println(greeting + "\n");
Integer[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int sum = Arrays.stream(numbers).reduce(0, (x, y) -> x + y);
// or with .reduce(0, Integer::sum);
System.out.println("Sum of Array: " + sum);
System.out.println("\n");
// Reduce List to sum.
List<Integer> list = Arrays.asList(numbers);
sum = list.stream().reduce(0, (x, y) -> x + y);
System.out.println("Sum of List: " + sum);
List<Integer> list2 = Arrays.asList(2, 3, 4);
// Here result will be 2*2 + 2*3 + 2*4 that is 18.
int res = list2.parallelStream().reduce(2, (s1, s2) -> s1 * s2, (p, q) -> p + q);
System.out.println(res);
}
public static String greet(List<String> names) {
String greeting = names.stream().map(name -> name + " ").reduce("Welcome ", (acc, name) -> acc + name);
return greeting + "!";
}
output:
Jack | Steve | Alice
Jack,Steve,Alice
Welcome Jack Steve Alice !
Sum of Array: 55
Sum of List: 55
18