package com.mayikt.stream;  import java.util.Optional; import java.util.function.BinaryOperator; import java.util.stream.Stream;  /**  * @ClassName Test10  * @Author 蚂蚁课堂余胜军 QQ644064779 www.mayikt.com  * @Version V1.0  **/ public class Test10 {     public static void main(String[] args) {         Stream integerStream = Stream.of(10, 20, 30);         Optional reduce = integerStream.reduce(new BinaryOperator() {             @Override             public Integer apply(Integer a1, Integer a2) {                 return a1 + a2;             }         });         System.out.println(reduce.get());     } }