package Java8Study.optional;

import Java8Study.lambda1.Employee;

import org.junit.Test;

import java.util.Optional;

public class TestOptional {

/**

* Optional 容器类的常用方法

*/

@Test

public void test1(){

//of 封装对象

Optional<Employee> op = Optional.of(new Employee());

//get获取对象

Employee employee = op.get();

System.out.println(employee);

//isPresent 判断是否有值

if(op.isPresent()){

op.get();

}

//orElse(T t) 如果对象有值返回值，没有则返回 T t

Employee emp = op.orElse(new Employee());

//此时不用get()获取了，因为返回的直接就是T类对象

System.out.println(emp);

//orElseGet(Supplier s) 如果调用对象包含值，返回该值，否则返回 s 获取的值

//函数式接口

Optional<Employee> op2 = Optional.ofNullable(null);

Employee emp2 = op.orElseGet(() -> new Employee());

System.out.println(emp2);

}

//创建空的optional

@Test

public void test2(){

//empty 创建空的实例，即该 op对象是空的

Optional<Employee> opEmpty = Optional.empty();

//ofNullable

Optional<Employee> opOfNullable = Optional.ofNullable(null);

System.out.println(opOfNullable.get());

}

//map(Function f) :如果有值，对其处理并返回处理后的Optional，否则返回empty

//flatmap

@Test

public void test3(){

Optional<Employee> op = Optional.ofNullable(

new Employee("zhangsan",18,2313.12, Employee.Status.BUSY));

Optional<String> strOp = op.map( e -> e.getName());

System.out.println(strOp.get());

Optional<String> strOp2 = op.flatMap(e -> Optional.of(e.getName()));

System.out.println(strOp2.get());

}

}