On my previous job, providing all methods with javadoc was mandatory, which resulted in things like:
/**
* Sets the Frobber.
*
* @param frobber The frobber
*/
public setFrobber(Frobber frobber) { ... }
As you can see, the documentation takes up space and work, but adds little to the code.
Should documenting all methods be mandatory or optional? Is there a rule for which methods to document? What are pros and cons of requiring every method to be documented?
For big projects or frameworks/libraries or even open source project that you are creating, it is mandatory. For small personal or private projects it is optional. Having said that, it is always a good idea to document your code so if you come back to your project after a year whether small or big, you know what it was doing. This really helps greatly.
You should always document your code. especially if someone else work or will work on your code. Maybe you didn't have a chance yet to work on legacy not-documented code but it can be a real pain!
About the comment itself, one thing to avoid is writing a comment because it is mandatory, Just think a few second and you'll find something to tell about your method, something that's not already in the method name, something that might not be obvious to the next developer. Explain what your method does, what are the corner cases, what it expect as input.
And remember :
Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.
it applies to comments too :)
It's much easier to maintain "self-documenting" code. If you choose good function and variable names, keep functions short (eg. < 10 lines with only a single idea per function), this will help keep the purpose of the code clear. And you won't have to try to keep the comments up to date - the only thing worse than no comments is comments that are wrong!
There's a good and recent summary of various points of view at InfoQ.
Documentation of code is very important. But Javadoc (or similar tools) are not the only and not the best method for this. The biggest downside is, that Javadoc-documentation must be kept up to date. If the method is changed, but the description stays the same, this documentation can do more trouble than good.
To avoid the problem with documentation not in sync with the code, use code to document. Unit-tests show how your code is used and asserts in the code can ensure that parameters and return-values are validated. In a project I added asserts to a calculation, that the probabilities in this calculation are always between 0 and 1. Later this assert triggered in a use case and pointed me directly to a bug.
The most important documentation is a good naming. If you set a Frobber, then setFrobber is a good name. The Javadoc given in your example adds nothing to this naming. frobIt would be a not so good name, method3 would be very bad. Code reviews should help to get good naming.
Javadocs and ither documentation should be added, if the other methods aren't sufficient. But in this case you need to take care, that this documentation is always up to date.
"providing all methods with javadoc was mandatory"
I strongly suspect that documenting all methods was mandatory, but providing javadoc comments was all that could be automatically enforced and hence all that was uniformly done.
Personally I think it's better to have no javadoc than completely useless javadoc - at least you can see from a glance at the HTML which methods are undocumented, because there are no descriptions of the parameters etc.
Documentation is frequently underrated, because it always seems less important and urgent when you're writing the code, than it does when you're using it later. But the style and form of documentation is often overrated - auto-generated XML nonsense is still nonsense. Given the choice, I'd rather have the code comment // Sets this object to use the specified frobber for all future frobbing, than your zero-information javadoc.
For all I know from your docs, the function doesn't actually modify this object at all, it might call the set() function on frobber, or it might be while(!frobber.isset()) { refrigerator.add(frobber); sleep(3600); refrigerator.remove(frobber); } Hence it "sets the frobber". I'm sure I read somewhere that "set" is the word with the most distinct definitions in the OED. Brief descriptions are ambiguous and hence misleading, and the purpose of documentation is to stop people relying on your source, and hence on details of your current implementation. My comment doesn't really take any longer to write than it took to add "Sets the frobber" and "the frobber" to the IDE-generated javadoc stub. It doesn't explain what frobbing is or when this object does it (hopefully that's elsewhere in the class docs) but at least it tries to tell you what the function does.
As for when to mandate documentation - I think every interface must be documented. If you're not defining Java interface s, the "interface" is every public and protected method, and every package-protected method unless the package is tiny. Implementation doesn't have to be documented, although it should be commented if the way it works is non-obvious. Documentation might be as simple as the sentence in my comment above - you don't necessarily need a separate sentence for each parameter if the method description already says what they are.
If you have code review, then IMO the answer is to review comments and documentation at the same time. If you don't have code review, then you need a cone of shame for whichever developer most recently forced someone else to come over and ask what the code actually does.
The same applies to anyone who relied on undocumented behaviour of a function, with a result that an implementation change that didn't change the interface, breaks their code. The way you enforce that code be documented, is to complain that you can't call it until you know what it guarantees to do. Arbitrary rules like, "javadoc comments must exist" become less important, at least for functions that other developers need to call.
Q: Should documenting all methods be mandatory or optional?
A: Mandatory.
Q: Is there a rule for which methods to document?
A: All of them.
Q: What are pros and cons of requiring every method to be documented?
A: Pros: Smart people can spend time focusing on code writing, not code figuring-out. Code is well explained. Code can be passed to newbies. Cons: Whining. Stale comments.
A focus on quality commenting obviates the 'code is self-documenting' issues.
In the case of getters and setters, not every get and set is trivial. Sometimes it is, that's great. When it isn't, the comment should note the information. It's better to be conservative and always have comments than unconservative and have to scrap code and waste time figuring it out.
Final example: The Carmack Inverse Square Root code. Self-documenting, eh?
