Boolean method naming readability

Question

Simple question, from a readability standpoint, which method name do you prefer for a boolean method:

public boolean isUserExist(...)

or:

public boolean doesUserExist(...)

or:

public boolean userExists(...)

Answer 1

The goal for readability should always be to write code the closest possible to natural language. So in this case, userExists seems the best choice. Using the prefix "is" may nonetheless be right in another situations, for example isProcessingComplete.

Answer 2

public boolean userExists(...)

Would be my prefered. As it makes your conditional checks far more like natural english:

if userExists ...

But I guess there is no hard and fast rule - just be consistent

Answer 3

Purely subjective.

I prefer userExists(...) because then statements like this read better:

if ( userExists( ... ) )

or

while ( userExists( ... ) )

Answer 4

I would go with userExists() because 1) it makes sense in natural language, and 2) it follows the conventions of the APIs I have seen.

To see if it make sense in natural language, read it out loud. "If user exists" sounds more like a valid English phrase than "if is user exists" or "if does user exist". "If the user exists" would be better, but "the" is probably superfluous in a method name.

To see whether a file exists in Java SE 6, you would use File.exists(). This looks like it will be the same in version 7. C# uses the same convention, as do Python and Ruby. Hopefully, this is a diverse enough collection to call this a language-agnostic answer. Generally, I would side with naming methods in keeping with your language's API.

Answer 5

I like any of these:

userExists(...)
isUserNameTaken(...)
User.exists(...)
User.lookup(...) != null

Answer 6

I would say userExists, because 90% of the time my calling code will look like this:

if userExists(...) {
  ...
}

and it reads very literally in English.

if isUserExist and if doesUserExist seem redundant.