JAVA8特性：Optional使用方法

目录

​​常见场景​​

​​demo​​

传统 Java 的写法显得冗长难懂，而新的 ​​Optional<T>​​ +Lambda 则清新脱俗

常见场景

demo

package com.nio4444.demo.java8;

import com.google.common.collect.Lists;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import java.util.stream.Collectors;

public class MethodRefDemo {
    public static void main(String[] args) {

        Supplier<Person> personSupplier = Person::new ;
        Person p1 = new Person(1,"q1",0);
        Person p2 =  personSupplier.get() ;

        System.out.println(p1.getName());
        System.out.println(p2.getName());


        Optional<Person> p = Optional.ofNullable(p1) ;
        String result = p.map(p3->p3.getName())
                .map(name->name.toUpperCase())
                .orElse(null) ;
        System.out.println(result);

        p = Optional.ofNullable(p2) ;
        String result2 = p.map(p3->p3.getName())
                .map(name->name.toUpperCase())
                .orElse(null) ;
        System.out.println(result2);

    }
}

@Data
@NoArgsConstructor
@AllArgsConstructor
class Person implements Serializable {
    private int age ;
    private String name ;
    private int mark ;

    public static Person create(final Supplier<Person> s) {
        return s.get() ;
    }
}