difference between null != something and something != null

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??

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

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.

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.

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

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.

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

They are both the same there is no difference.

来源：https://stackoverflow.com/questions/14578703/difference-between-null-something-and-something-null

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null-check