Java新特性Opitional

Java8中Optional的一些方法

具体操作

public class Girl {
    private String name;

    public Girl() {
    }

    public Girl(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Girl{" +
                "name='" + name + '\'' +
                '}';
    }
}

public class Boy {

    private Girl girl;

    public Boy(){

    }

    public Boy(Girl girl){
        this.girl = girl;
    }

    public Girl getGirl() {
        return girl;
    }

    public void setGirl(Girl girl) {
        this.girl = girl;
    }
}

创建Optional类对象的方法

    @Test
    public void test1(){
        Girl girl = new Girl();
        //保证t是非空的
        Optional<Girl> optionalGirl = Optional.of(girl);
    }

    @Test
    public void test2(){
        Girl girl = new Girl();
        girl = null;
        //t可以为null
        Optional<Girl> optionalGirl = Optional.ofNullable(girl);
        System.out.println(optionalGirl);

    }

以前写代码会出现空指针

    public String getGirlName(Boy boy){
        return boy.getGirl().getName();
    }

    @Test
    public void test3(){
        Boy boy = new Boy();
        String girlName = getGirlName(boy);
        System.out.println(girlName);
    }

优化后的代码

    //优化以后的getGirlName();
    public String getGirlName1(Boy boy){
        if (boy != null){
            Girl girl = boy.getGirl();
            if (girl != null){
                return girl.getName();
            }
        }
        return null;
    }

    @Test
    public void test4(){
        Boy boy = new Boy();
        String girlName = getGirlName1(boy);
        System.out.println(girlName);
    }

使用Optional代码进行优化

    //Optional优化以后的getGirlName();
    public String getGirlName2(Boy boy){
        Optional<Boy> optionalBoy = Optional.ofNullable(boy);
        //boy1一定非空
        Boy boy1 = optionalBoy.orElse(new Boy(new Girl("贾斯汀")));
        Girl girl = boy1.getGirl();
        Optional<Girl> girlOptional = Optional.ofNullable(girl);
        //girl1一定非空
        Girl girl1 = girlOptional.orElse(new Girl("虎牙"));
        return girl1.getName();
    }

    @Test
    public void test5(){
        Boy boy = null;
        String girlName = getGirlName2(boy);
        System.out.println(girlName);
    }

Java9中Opitonal类中使用stream()的使用

Java11中Optional新增的方法