java8之Optional案例

import entity.Student;

import java.util.Optional;

public class OptonalDemo {
    public static void main(String[] args) throws Exception {
        Student student = new Student();
        Optional student1 = Optional.of(student);

        Student student2 = null;
        Optional opt = Optional.ofNullable(student2);
        // 用 isPresent  判断 optional中的对象是否为空
        if(opt.isPresent()) {
            System.out.println("optional 不为空");
            // optional 使用 get 获取 里面的对象
            Student student3 = opt.get();
        } else {
            System.out.println("optional 为空");

        }

    }


}

import entity.Student;

import java.util.Optional;

public class OrElseDemo {
    public static void main(String[] args) throws Exception {

        Student student = null;
        Student student2 = new Student();
        student2.setAge(10);
        student2.setName("李洪伟");
        // orelse兜底对象， 如果前面为空，则返回兜底对象
        Student student1 = Optional.ofNullable(student).orElse(student2);
        System.out.println(student1);


        Integer age = Optional.ofNullable(student2).map(obj -> obj.getAge()).orElse(7);
        System.out.println("age1:" + age);
        Integer age2 = Optional.ofNullable(student).map(obj -> obj.getAge()).orElse(7);
        System.out.println("age1:" + age2);
    }


}