Question

I’m working on a java source code that has the style:

if (0 == var) {}
and 
if (null == someObj) {}

or

if (0 != var) {}
and 
if (null != someObj) {}

Should I rewrite it to:

if (var == 0) {}
and 
if (someObj == null) {}

?

Thanks in advance!.

Answer 1

It’s perfectly valid to have:

if (0 == var) {}
and 
if (null == someObj) {}

It’s famously called yoda condition to prevent accidental use single = in place of ==.

I personally never used it. But some people like it. It’s really a matter of taste.

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However, it’s of no use in Java. Because, such an accidental typo is caught at compile time.

The following would give a compile time error in Java.

if( var = 0 ) 
{
//Some code
}

Because assignment operation doesn’t yield Boolean value in Java.
However, in languages like C/C++, the above is valid and compiler would give no errors if warnings are not enabled. The above if condition will always evaluate to false (0) in C/C++. So it may go unnoticed and give unexpected results at run time.

In GCC, with all warnings enabled, it would give the warning for the above in C or C++:

warning: suggest parentheses around assignment used as truth value

So this may not of much use in C/C++ too as one is expected to compile with all warnings and fix all warnings. As I said before it’s a personal choice and makes no difference.

So if ( 0 == var){} is a valid syntax and is same as if (var == 0) {} and if you prefer Yoda conditions it, go for it!