Is it bad to explicitly compare against boolean constants e.g. if (b == false) in Java?

Question

Is it bad to write:

if (b == false) //...  while (b != true) //... 

Is it always better to instead write:

if (!b) //...  while (!b) //... 

Presumably there is no difference in performance (or is there?), but how do you weigh the explicitness, the conciseness, the clarity, the readability, etc between the two?

Update

To limit the subjectivity, I'd also appreciate any quotes from authoritative coding style guidelines over which is always preferable or which to use when.

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Note: the variable name b is just used as an example, ala foo and bar.

Answer 1

It's not necessarily bad, it's just superfluous. Also, the actual variable name weights a lot. I would prefer for example if (userIsAllowedToLogin) over if (b) or even worse if (flag).

As to the performance concern, the compiler optimizes it away at any way.

As to the authoritative sources, I can't find something explicitly in the Java Code Conventions as originally written by Sun, but at least Checkstyle has a SimplifyBooleanExpression module which would warn about that.

Answer 2

You should not use the first style. I have seen people use:

• if ( b == true )
• if ( b == false )

I personally find it hard to read but it is passable. However, a big problem I have with that style is that it leads to the incredibly counter-intuitive examples you showed:

• if ( b != true )
• if ( b != false )

That takes more effort on the part of the reader to determine the authors intent. Personally, I find including an explicit comparison to true or false to be redundant and thus harder to read, but that's me.