空安全方法调用 Java7
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Null-safe Method invocation Java7
提问by Subodh Joshi
I want to get details about this feature of Java7 like this code
我想像这段代码一样获取有关 Java7 的此功能的详细信息
public String getPostcode(Person person)
{
if (person != null)
{
Address address = person.getAddress();
if (address != null)
{
return address.getPostcode();
}
}
return null;
}
Can be do something like this
可以做这样的事情
public String getPostcode(Person person)
{
return person?.getAddress()?.getPostcode();
}
But frankly its not much clear to me.Please explain?
但坦率地说，我不太清楚。请解释一下？
采纳答案by Rohit Jain
Null-safe method invocation was proposed for Java 7 as a part of Project Coin, but it didn't make it to final release.
作为 Project Coin 的一部分，为 Java 7 提出了空安全方法调用，但它没有最终发布。
See all the proposed features, and what all finally got selected here - https://wikis.oracle.com/display/ProjectCoin/2009ProposalsTOC
查看所有提议的功能，以及最终在此处选择的所有功能 - https://wikis.oracle.com/display/ProjectCoin/2009ProposalsTOC
As far as simplifying that method is concerned, you can do a little bit change:
就简化该方法而言，您可以做一些更改：
public String getPostcode(Person person) {
if (person == null) return null;
Address address = person.getAddress();
return address != null ? address.getPostcode() : null;
}
I don't think you can get any concise and clearer than this. IMHO, trying to merge that code into a single line, will only make the code less clear and less readable.
我认为没有比这更简洁明了的了。恕我直言，试图将该代码合并为一行，只会使代码变得不那么清晰和可读性较差。
回答by Kon
If I understand your question correctly and you want to make the code shorter, you could take advantage of short-circuit operators by writing:
如果我正确理解您的问题并且您想缩短代码，您可以通过编写以下内容来利用短路运算符：
if (person != null && person.getAddress() != null)
return person.getAddress().getPostCode();
The second condition won't be checked if the first is false because the && operator short-circuits the logic when it encounters the first false.
如果第一个条件为假，则不会检查第二个条件，因为 && 运算符在遇到第一个时会短路逻辑false。
回答by Eldar Agalarov
It should work for you:
它应该适合你：
public String getPostcode(Person person) {
return person != null && person.getAddress() != null ? person.getAddress().getPostcode() : null;
}
Also check this thread: Avoiding != null statements
还要检查这个线程：Avoiding != null statements
回答by radiantRazor
If you want to avoid calling getAddress twice, you can do this:
如果你想避免调用 getAddress 两次，你可以这样做：
Address address;
if (person != null && (address = person.getAddress()) != null){
return address.getPostCode();
}
