Question

Consider the following two lines of code

if (test ! = null)

and

if (null != test)

Is there is any difference in above two statements, performance wise? I have seen many people using the later and when questioned they say its a best practice with no solid reason.

Answer 1

No difference.

Second one is merely because C/C++ where programmers always did assignment instead of comparing.

E.g.

// no compiler complaint at all for C/C++
// while in Java, this is illegal.
if(a = 2) {
}
// this is illegal in C/C++
// and thus become best practice, from C/C++ which is not applicable to Java at all.
if(2 = a) {
}

While java compiler will generate compilation error.

So I personally prefer first one because of readability, people tend to read from left to right, which read as if test is not equal to null instead of null is not equal to test.