用Java 8可选替换null检查 [英] Replacing null check with java 8 optional

问题描述

我正在尝试用可选的代码块替换下面的代码块，只是想检查这样做是否会对性能或诸如此类的事情产生不良影响?

I am trying to replace below code block with optional, just want to check will there be any bad implications of doing this like performance or anything as such?

现有代码:

UserObj userObj=new UserObj();
Object result = fetchDetails();
if (null != result) {
    userObj.setResult(result.toString());
}

使用Java 8 Optional:

UserObj userObj=new UserObj();
Optional.ofNullable(fetchDetails()).ifPresent(var -> userObj.setResult(var.toString()));

进行此更改只是为了使代码看起来简洁，因为我的代码中有很多空检查块.

Doing this change just to make code look concise as there are lot of null check blocks in my code.

推荐答案

首先，我认为您误解了Optional的目的.不仅仅是替换

First of all I think you're misunderstanding the purpose of Optional. It is not just for replacing

if(obj != null){ ... }

Optional的要点是为函数返回值提供一种手段，以指示不存在返回值.请阅读这篇文章以了解更多详细信息.

The main point of Optional is to provide a means for a function returning a value to indicate the absence of a return value. Please read this post for more details.

在您的情况下正确使用Optional将会从fetchDetails方法返回可选的ResultObj:

The proper use of Optional in your case would be returning optional ResultObj from fetchDetails method:

Optional<ResultObj> fetchDetails() {
   ...
}

然后，您只需像以前一样简单地将方法链接在获取的Optional上即可.

Then you simply chain the methods on fetched Optional as you did before.

更新

如果您无法修改fetchDetails，仍然可以选择将其包装到您自己的方法中，如下所示:

In case you cannot modify fetchDetails there is still an option of wrapping it into your own method like the following:

Optional<ResultObj> fetchOptionalDetails() {
    return Optional.ofNullable(fetchDefails());
}

创建一个新方法将增加很小的开销，但是代码将更具可读性:

Creating a new method will add a tiny overhead, but the code will be much more readable:

fetchOptionalDetails().ifPresent(details -> /* do something */);

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