将老式转换为 Optional.ifPresent() 时出现问题

Question

我在将老式转换为Optional.ifPresent. 这是之前版本的代码。

State state = State.OK;

final Optional<Person> checkExistingPerson = checkIt();

if(checkExistingPerson.isPresent()) {

    Person person = checkExistingPerson.get();

    if("blah".equals(person.getName())) {

        state = State.DUPLICATE;

    } else {

        state = State.RESTORED;

    }

    return Member(person.getId(), state);

}

return Member(null, state);

这是Optional.ifPresent用法

State state = State.OK;

final Optional<Person> checkExistingPerson = checkIt();

checkExistingPerson.ifPresent(person -> {

    if("blah".equals(person.getName())) {

        state = State.DUPLICATE;

    } else {

        state = State.NEW;

    }

    return Member(person.getId(), state);

});

return Member(null, state);

而且，这是 IntelliJ 强迫我更改它的屏幕截图。

Optional关于我的问题，最好的方法是什么？谢谢！

Answer 1

您不能从 lambda 表达式中更改局部变量的值。此外，ifPresent不能返回值，因为它的返回类型是void.相反，您应该使用Optional.map，Optional如果它存在，它会转换被包装的对象：return checkExistingPerson&nbsp; &nbsp; .map(person -> new Member(&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; person.getId(),&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; "blah".equals(person.getName()) ? State.DUPLICATE : State.RESTORED))&nbsp; &nbsp; .orElse(new Member(null, State.OK));