Using NOT operator in IF conditions

Question

Is it really a good practice to avoid using NOT operator in IF conditions in order to make your code better readable? I heard the if (doSomething()) is better t

Answer 1

It is generally not a bad idea to avoid the !-operator if you have the choice. One simple reason is that it can be a source of errors, because it is possible to overlook it. More readable can be: if(conditionA==false) in some cases. This mainly plays a role if you skip the else part. If you have an else-block anyway you should not use the negation in the if-condition.

Except for composed-conditions like this:

if(!isA() && isB() && !isNotC())

Here you have to use some sort of negation to get the desired logic. In this case, what really is worth thinking about is the naming of the functions or variables. Try to name them so you can often use them in simple conditions without negation.

In this case you should think about the logic of isNotC() and if it could be replaced by a method isC() if it makes sense.

Finally your example has another problem when it comes to readability which is even more serious than the question whether to use negation or not: Does the reader of the code really knows when doSomething() returns true and when false? If it was false was it done anyway? This is a very common problem, which ends in the reader trying to find out what the return values of functions really mean.