Java8中的新特性Optional

package com.demo.optional;

import lombok.extern.slf4j.Slf4j;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.Optional;

@Slf4j
@RunWith(SpringRunner.class)
@SpringBootTest
public class TestOptional {

    @Test
    public void testOptional() {
        TestOptional test = new TestOptional();
        Integer value1 = null;
        Integer value2 = new Integer(10);

        // Optional.ofNullable - 允许传递为 null 参数
        Optional<Integer> a = Optional.ofNullable(value1);

        // Optional.of - 如果传递的参数是 null，抛出异常 NullPointerException
        Optional<Integer> b = Optional.of(value2);
        log.info("{}", test.sum(a, b));
    }

    public Integer sum(Optional<Integer> a, Optional<Integer> b) {
        // Optional.isPresent - 判断值是否存在
        log.info("第一个参数值存在: {}", a.isPresent());
        log.info("第二个参数值存在: {}", b.isPresent());

        // Optional.orElse - 如果值存在返回它，否则返回默认值
        Integer value1 = a.orElse(new Integer(0));

        //Optional.get - 获取值，值需要存在
        Integer value2 = b.get();

        return value1 + value2;
    }
}