difference between null != something and something != null

Question

Is there a difference between null != something and something != null in Java. And if there is a difference then which one should I use and why??

It's called yoda condition. I answered [why it's not-so-useful in Java](http://stackoverflow.com/questions/13887559/is-it-appropiate-the-statement-if-0-expression-or-variable-in-java/13887579#13887579) but somewhat used in C/C++ etc. — P.P, Jan 29 '13 at 08:49

score 5 · Answer 1 · answered Jan 29 '13 at 08:44

There's no difference between null != something and something != null. You must be thinking about the person.getName().equals("john") and the "john".equals(person.getName()) difference: the first one will throw a NullPointerException if getName() returns null, while the second won't. But this is not applicable for the example of your question.

score 5 · Answer 2 · answered Jan 29 '13 at 08:44

5

its probably comming from the so-called joda-conditions where you write "bla" == myVariable instead of myVariable == "bla" because it could happen to accidentially write myVariable = "bla" which returns "bla" in some languages but also assign "bla" to myVariable

answered Jan 29 '13 at 08:44

wrm

1,898
13
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Thank you! A colleague of mine explained it to me, and I couldn't remember what she had said! – Nathan White Jan 29 '13 at 08:47

score 4 · Answer 3 · answered Jan 29 '13 at 09:39

I just want to point out that the "Yoda condition" rationale for doing this (in languages like C & C++) does not apply in this (Java) case.

Java does not allow general expressions to be used as statements, so both
```
 something == null;
```
and
```
 null == something;
```
would be compilation errors.
The types of something == null and something = null are different; boolean and some reference type respectively. In this case, it means that both:
```
 if (something = null) {
     ...
 }
```
and
```
 if (null = something) {
     ...
 }
```
would be compilation errors.

In fact, I can't think of a realistic example where null == something would be compilation error and something == null would not. Hence, it doesn't achieve anything in terms of mistake-proofing.

That's also the case in C#. Mistakenly used "=" in a boolean condition instead of "==" results in a compilation error. Yoda condition does nothing here. — Jürgen Bayer, Aug 02 '13 at 06:07

score 1 · Answer 4 · answered Jan 29 '13 at 08:42

1

There is no difference, but some people use it for ease of readability in their code.

answered Jan 29 '13 at 08:42

Nathan White

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score 1 · Answer 5 · answered Jan 29 '13 at 08:45

Point of view of performance there will be no difference, both sides of the operator are executed any way. But for a more readable code second one seems more readable

  obj.getSomething().getAnotherThing().doSomething() != null

  null != obj.getSomething().getAnotherThing().doSomething()

But if you are going to just compare a variable or parameter this is more readable

  something != null

Of course this depends on sense of reader.

score 0 · Answer 6 · answered Jan 29 '13 at 08:45

0

In java if we compare any, always we have to place variables at left hand side and values are placed at right hand side...

answered Jan 29 '13 at 08:45

Naveen Kumar Alone

7,536
5
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1

I think that is convention. – Subhrajyoti Majumder Jan 29 '13 at 08:46

score 0 · Answer 7 · answered Jan 29 '13 at 08:45

0

They are both the same there is no difference.

answered Jan 29 '13 at 08:45

CloudyMarble

36,908
70
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difference between null != something and something != null

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