Optional解决链式调用NPE问题

1.map()

public class Main {
    public static void main(String[] args) {
        Person person = new Person();
        Info personInfo =new Info();
        int result;

        // 1.PersonInfo 为空
        person.setPersonInfo(null);
        result = Optional.ofNullable(person)
                .map(Person::getPersonInfo)
                .map(Info::getAge)
                .orElse(-1);
        System.out.println("PersonInfo为空, result is " + result);


        //2.PersonInfo.age 为空
        person.setPersonInfo(personInfo);
        result = Optional.ofNullable(person)
                .map(Person::getPersonInfo)
                .map(Info::getAge)
                .orElse(-1);
        System.out.println("PersonInfo.age为空, result is " + result);


        // 3.非空
        personInfo.setAge(1);
        person.setPersonInfo(personInfo);
        result = Optional.ofNullable(person)
                .map(Person::getPersonInfo)
                .map(Info::getAge)
                .orElse(-1);
        System.out.println("非空, result is " + result);
    }
}

结果：

2.filter()

public void setName(String name) throws IllegalArgumentException {
    this.name = Optional.ofNullable(name).filter(User::isNameValid)
                        .orElseThrow(()->new IllegalArgumentException("Invalid username."));
}