Difference between null==object and object==null [duplicate]

问题

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' … != null' or 'null != …' best performance? (16 answers)

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Hi I would like to know diff between the above comparisons?

I am getting null pointer exception when I check object.getItems() == null. But if I change it to null == object.getItems(), it workes fine.

I did look into this what is the difference between null != object and object!=null But I didnt get satisfactory answer.

回答1:

^{(Similar question: Which is more effective: if (null == variable) or if (variable == null)?)}

Difference between null==object and object==null

There is no semantical difference.

object.getItems() == null and null == object.getItems() are equivalent.

Perhaps you're mixing it up with the fact that

nonNullObj.equals(obj)

and

obj.equals(nonNullObj)

can make a difference (since the second alternative could result in a NPE in case the callee is null).

来源：https://stackoverflow.com/questions/3004103/difference-between-null-object-and-object-null