Double null check in single line

Question

Is the following code the best way to check for null for two times in a single line for initializaing a final variable?

final String textValue = text != null ? text.getText() != null ? text.getText() : "" : "";

`text != null && text.getText() != null` - remember that `&&` and `||` short-circuit. Although, I would try to ensure that `text` can *never* be null and that `getText` can *never* return null, but perhaps that is just wishful thinking? — user2246674, Jun 17 '13 at 05:59
You can shorten it by doing `text != null && text.getText() != null ? text.getText() : "";` — Luiggi Mendoza, Jun 17 '13 at 05:59
If you fell this is amazingly easy to understand for your fellow programmers, then please go ahead;-) — Juned Ahsan, Jun 17 '13 at 06:00
[Checking if condition for 'null'](http://stackoverflow.com/questions/14787392/checking-if-condition-for-null) — Grijesh Chauhan, Jun 17 '13 at 06:00
It's not a TextBox. It's of TimedText type in Android and it can be null. — Mohsen Afshin, Jun 17 '13 at 07:10

score 8 · Accepted Answer · answered Jun 17 '13 at 05:59

8

Well I'd probably use a single conditional with an && condition instead:

final String textValue = text != null && text.getText() != null ? text.getText()
                                                                : "";

If you find you need to do this in more than one place, you may well want to wrap it in a method:

// We don't know what the type of text is here... adjust appropriately.
public static String getTextOrDefault(TextBox text, String defaultValue)
{
    return text != null && text.getText() != null ? text.getText()
                                                  : defaultValue;
}

Or adjusted to avoid calling getText() more than once:

// We don't know what the type of text is here... adjust appropriately.
public static String getTextOrDefault(TextBox text, String defaultValue)
{
    if (text == null)
    {
        return defaultValue;
    }
    String textValue = text.getText();
    return textValue != null ? text.getText() : defaultValue;
}

Then you can simplify your variable declaration:

final String textValue = SomeHelper.getTextOrDefault(text, "");

Note that whether calling text.getText() more than once is a problem depends on your scenario - in some cases it would be a bad idea, and you should restructure your code to avoid it. We can't tell for sure, but it's worth considering.

answered Jun 17 '13 at 05:59

Jon Skeet

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@Aubin Why not? For this case it's presumably fine - if it was a "long operation" or had side-effects, then no. – user2246674 Jun 17 '13 at 06:01
@Aubin: Maybe. Maybe not. We don't really know without knowing the class involved. – Jon Skeet Jun 17 '13 at 06:02
For performance reason, I don't knwon (and I don't want to know) how complex the method getText() is. In the "method" version the ternary should be replaced by two lines. – Aubin Jun 17 '13 at 06:03
@Aubin let the JIT handle this. – Luiggi Mendoza Jun 17 '13 at 06:03
@Aubin: I've edited the answer to give that option, but quite often simplicity triumphs *potential* (but unrealistic) performance concerns. For example, I'm happy enough calling `ArrayList.size()` in a loop. – Jon Skeet Jun 17 '13 at 06:04
@JonSkeet, you eat the SO Scores, and others must be very very fast to beat you :-). Nice answer. Thanks. – Mohsen Afshin Jun 17 '13 at 06:30

score 3 · Answer 2 · answered Jun 17 '13 at 06:00

3

You can do this :

final String textValue = (text != null && text.getText() != null) ? text.getText() : "" ;

answered Jun 17 '13 at 06:00

AllTooSir

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@Craig not only that. Jon even improved his answer by far than this one. – Luiggi Mendoza Jun 17 '13 at 06:02
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@LuiggiMendoza Then you can upvote his answer and downvote mine . I have stopped taking anything from self proclaimed moderators. – AllTooSir Jun 17 '13 at 06:04
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I don't need to downvote yours since somewhat answers OP's question. – Luiggi Mendoza Jun 17 '13 at 06:04
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@TheNewIdiot: No-one suggested downvoting - there's no need to be aggressive about it. – Jon Skeet Jun 17 '13 at 06:06
5

As usual - SO is friendly place to ask and a hostile place to answer ;-/ – tbsalling Jun 17 '13 at 06:06
@JonSkeet I say this because I feel stalked by some self proclaimed moderator . May be SO guys can figure this out from the recent activity ! – AllTooSir Jun 17 '13 at 06:06
1

@TheNewIdiot: Stack Overflow has millions of users. Being aggressive to everyone just because you've had a bad experience with some people really isn't a good strategy. – Jon Skeet Jun 17 '13 at 06:09
@JonSkeet Just like in real world ;) – Maroun Jun 17 '13 at 06:14

score 0 · Answer 3 · answered Jun 17 '13 at 06:01

0

I am not sure what you mean by "best" (most programmer friendly? most efficient execution?)

But a programmer friendly alternative could be:

final String textValue = (text != null && text.getText() != null) ? text.getText() : "";

answered Jun 17 '13 at 06:01

tbsalling

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score 0 · Answer 4 · answered Jun 17 '13 at 06:02

0

I assume this line is somewhere in a method. So this one will be more readable:

String value = "";
if (text != null && text.getText() != null) {
  value = text.getText();
}
final String textValue = value;

answered Jun 17 '13 at 06:02

Obenland

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Double null check in single line

4 Answers4