zoukankan      html  css  js  c++  java
  • Java8-Optional-No.02

    import java.util.Optional;
    import java.util.function.Supplier;
    
    public class Optional2 {
    
        static class Outer {
            Nested nested = new Nested();
    
            public Nested getNested() {
                return nested;
            }
        }
    
        static class Nested {
            Inner inner = new Inner();
    
            public Inner getInner() {
                return inner;
            }
        }
    
        static class Inner {
            String foo = "boo";
    
            public String getFoo() {
                return foo;
            }
        }
    
        public static void main(String[] args) {
            test1();
            test2();
            test3();
        }
    
        public static <T> Optional<T> resolve(Supplier<T> resolver) {
            try {
                T result = resolver.get();
                return Optional.ofNullable(result);
            }
            catch (NullPointerException e) {
                return Optional.empty();
            }
        }
    
        private static void test3() {
            Outer outer = new Outer();
            resolve(() -> outer.getNested().getInner().getFoo())
                    .ifPresent(System.out::println);
        }
    
        private static void test2() {
            Optional.of(new Outer())
                    .map(Outer::getNested)
                    .map(Nested::getInner)
                    .map(Inner::getFoo)
                    .ifPresent(System.out::println);
        }
    
        private static void test1() {
            Optional.of(new Outer())
                    .flatMap(o -> Optional.ofNullable(o.nested))
                    .flatMap(n -> Optional.ofNullable(n.inner))
                    .flatMap(i -> Optional.ofNullable(i.foo))
                    .ifPresent(System.out::println);
        }
    }
    
  • 相关阅读:
    loj 6035 「雅礼集训 2017 Day4」洗衣服
    BZOJ 3251 树上三角形
    UwrhrQNgRh
    百度之星2018资格赛1002题解
    [CF-676B]PYRAMID OF GLASSES
    【CF-371C】Hamburgers
    洛谷P1012拼数——字符串排序
    位运算详解及应用
    NOIP 2014 Day2 T1 无线网络发射器
    写代码要注意的几点(2)
  • 原文地址:https://www.cnblogs.com/bilaisheng/p/10210908.html
Copyright © 2011-2022 走看看