返回布尔值的Java 10 ifPresentOrElse

问题描述

我对如何正确执行此操作"感到困惑:

I am a little confused on "how to do this properly":

 // return true: if present and number of lines != 0
  boolean isValid(Optional<File> optFile) {
    return optFile.ifPresentOrElse(f -> return !isZeroLine(f), return false);
 }

 private boolean isZeroLine(File f)  {
    return MyFileUtils.getNbLinesByFile(f) == 0;
 }

我知道语法不正确且无法编译，但这仅是您了解的主意.

I know the syntax is not correct and not compiling, but it's just for you to get the idea.

如何将其转换为干净的代码"?即避免这样做:

How can I turn this into 'clean code'?i.e. avoid doing:

if (optFile.isPresent()) {//} else {//}

推荐答案

处理布尔值返回类型(很容易推断出 Predicate s)，一种方法是使用 Optional.filter :

Dealing with boolean return type(easily inferred Predicates), one way to do that could be to use Optional.filter :

boolean isValid(Optional<File> optFile) {
    return optFile.filter(this::isZeroLine).isPresent();
}

但是，然后使用 Optional s参数似乎是一种不好的做法.正如卡洛斯(Carlos)的评论所建议的那样，另一种实现方式可能是:

But, then using Optionals arguments seems to be a poor practice. As suggested in comments by Carlos as well, another way of implementing it could possibly be:

boolean isValid(File optFile) {
    return Optional.ofNullable(optFile).map(this::isZeroLine).orElse(false);
}

---

另一方面， ifPresentOrElse 是一种结构，用于执行与 Optional 值之类的存在对应的某些操作，例如:

---

On another note, ifPresentOrElse is a construct to be used while performing some actions corresponding to the presence of the Optional value something like :

optFile.ifPresentOrElse(this::doWork, this::doNothing)

相应的动作可能是-

private void doWork(File f){
     // do some work with the file
}

private void doNothing() {
     // do some other actions
}

这篇关于返回布尔值的Java 10 ifPresentOrElse的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！