Question

I am seeing this a lot in someone’s code: null-check conditions are written like this:

if (null == value)

rather than

if (value == null)

I don’t think there is any reason to have the null precede the operator in Java. Is there any benefit to doing it this way? Is this simply a case of a C++ programmer applying his skill to Java incorrectly, or am I missing something important?

Answer 1

This is a case of so-called “Yoda Conditions” (item #1). Although it is possible to rationalize them in C/C++, there is no reason to use them in Java.

In C/C++, expressions of any type can go into ifs and whiles. Writing

if (var = NULL) // No compile-time error in C/C++

instead of

if (var == NULL)

is a common error among novices. Yoda conditions were supposedly a remedy to address this problem, at the cost of “Yodifying” your code: C/C++ would trap assignments to NULL

if (NULL = var) // Compile-time error

but “reversed” NULL checks are OK:

if (NULL == var)

Since Java considers non-boolean expressions inside control blocks of if, while, and for to be errors, it would trap var = null in place of var == null, triggering an error. Therefore, there is no reason to give up readability by “Yodifying” your expressions.