Null-safe Method invocation Java7

Question

I want to get details about this feature of Java7 like this code

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

public String getPostcode(Person person)
{
    return person?.getAddress()?.getPostcode();
}

But frankly its not much clear to me.Please explain?

Why do you need to write it in a shorter way? It's easy to read and straightforward in your first example. — Kon, Aug 09 '13 at 17:56
I think that proposal is rejected for Java 7. Do you have a link for the official documentation? — c.s., Aug 09 '13 at 18:02
@c.s. check the question section someone given the link also i checked its somewhere else — Subodh Joshi, Aug 09 '13 at 18:03

Rohit Jain · Accepted Answer · 2013-08-09T18:08:59.983

14

Null-safe method invocation was proposed for Java 7 as a part of Project Coin, but it didn't make it to final release.

See all the proposed features, and what all finally got selected here - https://wikis.oracle.com/display/ProjectCoin/2009ProposalsTOC

As far as simplifying that method is concerned, you can do a little bit change:

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.

edited Aug 09 '13 at 18:08

answered Aug 09 '13 at 17:57

Rohit Jain

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@subodh. What do you mean by that? – Rohit Jain Aug 09 '13 at 18:02
Do you mean this feature is not available with java7 and we can not implement it yet? – Subodh Joshi Aug 09 '13 at 18:05
@subodh. Yes. Check that link in my answer. You will see what all features were added in Java 7 – Rohit Jain Aug 09 '13 at 18:06
Hmm so do you mean if Java7 will have this type of feature it will increase complexity of coder – Subodh Joshi Aug 09 '13 at 18:10
@subodh. Well, I'm not the right person to comment on this. I can't comment on why a feature was accepted, and why some were rejected. May be they felt it not so important to be added as an extra feature. May be this doesn't add much value to the language. – Rohit Jain Aug 09 '13 at 18:13
Why wouldn't just try/catching a NPE here be cleaner? – Eurig Jones Sep 05 '14 at 20:10

score 1 · Answer 2 · answered Aug 09 '13 at 17:58

1

If I understand your question correctly and you want to make the code shorter, you could take advantage of short-circuit operators by writing:

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.

answered Aug 09 '13 at 17:58

Kon

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4

Except you evaluate `person.getAddress()` twice :( – arshajii Aug 09 '13 at 18:00
3

@Gamb No, it's not a question of optimization (although that could also come into play if `getAddress()` took a long time, but persumably it doesn't). This code is not the same as the OP's code. – arshajii Aug 09 '13 at 18:02
@Gamb If `getAddress()`'s body involves substantial amounts of processing, a second call would be undesirable. Without knowing the method's implementation, we can't make assumptions about the optimization quality of one call versus two calls. – FThompson Aug 09 '13 at 18:04
For the record, I would never write code like my answer here. I would prefer the code the OP wrote originally. But if his question is regarding a strictly shorter way of writing something, then my reply should be helpful in some way. HOPEFULLY. – Kon Aug 09 '13 at 18:05
@Vulcan I asked that before realizing the slight difference in the code. Still, if we can't assume in one way, we shouldn't be so hasty as to consider the other one more valid. – Fritz Aug 09 '13 at 18:07
You're missing a last line: `return null;` (or `else return null;`) – bacar Oct 03 '14 at 17:49

score 0 · Answer 3 · edited May 23 '17 at 10:29

0

It should work for you:

public String getPostcode(Person person) {
    return person != null && person.getAddress() != null ? person.getAddress().getPostcode() : null;
}

Also check this thread: Avoiding != null statements

edited May 23 '17 at 10:29

Community

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answered Aug 09 '13 at 18:01

Eldar Agalarov

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@NotNull will supported by Java7 – Subodh Joshi Aug 09 '13 at 18:01

score 0 · Answer 4 · answered Jul 17 '18 at 13:18

0

If you want to avoid calling getAddress twice, you can do this:

Address address;
if (person != null && (address = person.getAddress()) != null){
      return address.getPostCode();
}

answered Jul 17 '18 at 13:18

radiantRazor

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Null-safe Method invocation Java7

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