jalview

I know the problems you had with close() - you mentioned in the comments on the issue. However, you might have noticed that FileParse.close() is not called from many places, so changing its behaviour wouldn't have too many side effects.

The intended pattern for FileParse.close() was:

ParserThing pt;
try {
pt = new <? assignable to FileParse>(data spec..)
.. do whatever needed to trigger parsing
.. then check pt's error/warning status and report any problems.
} catch (IOException ..) {
.. handle read or parse errors 
}
finally {
if (pt!=null) {
pt.close();
} // catch and report any IOErrors if desired
}

I tried this first, but FileParse.close() deliberately leaves the FileParse in an error state, which caused problems later (I don't remember the specifics). I could not work out why the FileParse.close() was designed to do this but suspect changing this methos so it's (in general) not left in an error state will cause bigger problems. Also, since Jalview is used to having dataIn for the lifetime of the alignment, I wasn't sure if nulling the object would cause unforeseen errors (in e.g. filename etc).

Maybe it would be best to overload FileParse.close() to pass in an error value/message, then it would essentially be calling FileParse.closeDataIn() instead of FileParse.dataIn.close()

Agree with the finally {} – forgot that (not been a java programmer for quite long enough!). Presumably that should go in FileParse and not AlignFile too.

Ideally, any low level file ops should happen in the base class (FileParse) rather than here. AlignFile should call the FileParse.close() method rather than directly manipulate dataIn, which is managed by FileParse. Note that FileParse.close() nulls the dataIn reference so the stream can be garbage collected properly.

It's also good practice to try to close() in a finally {} clause, catching and reporting exceptions if needed... this is actually what the FileParse.close() method's design was intended for, since the caller should have already checked 'error' and 'errormessage' for parsing problems. Exceptions/Errors on close are not fatal for file import.

SequencesInfo which is an individual object is doable, but I feel like it would be just a wrapper around a Map. What additional functionality would SequencesInfo have over a traditional Map?

I'm not very familiar with serialization in java, I know there are libraries that can serialize beans to json or xml, but what are your expectations in this case?

one class with a static factory method seems to be better than two classes and an external mutable object.

What's wrong with static classes? They are just like regular classes but within other class' namespace. That's non-static inner classes that are special.
About factory pattern, I think it would be an overkill for a class that is only used by SeqsetUtils' methods.

yes, I see that, but do you really need a nested static class ? in line with my general comments re encapsulating the Map<String,SequenceInfo> further: perhaps it might make sense to simply apply a factory pattern rather than have an internal bean that a generic map holds references to ?

(lets not get stuck on this though, the main thing is that the implementation works fine for now, though needs more work in order to save/restore sequenceInfo objects from Jalview project files)

Because it's instantiated in a static context e.g. uniquify and it does not need an instance of SeqsetUtils object to work.

we won't see this messages unless asserts are enabled. Cache.log.warn is perhaps better ?