More efficient? No, I don't recall ever hearing that one.
Putting equality comparisons back-to-front is something that is usually done to avoid accidentally doing an assignment, by mis-typing "=" where you meant "==". By putting the constant (e.g. null) first, you make this mis-typing cause a compilation error, which is good, because it alerts you earlier to your mistake. It is more important in C and C++ than
Java, because the mis-typed expression is more likely to be legal in C/C++ than in Java.
Having decided to do equality tests back-to-front, some people decide to do all tests back-to-front, for consistency. Dunno if I agree with that.
[ October 20, 2005: Message edited by: Peter Chase ]