BlockingQueue implementation and other interfaces

[pschichtel]

I quickly build a BlockingQueue<byte[]> (gist here) based on the QueueFile for a project where I intend to use tape as an offline buffer/resend queue in case the uplink goes down. I could have just build the minimal wrapper I needed, but I though "why not just implement BlockingQueue and see if someone else thinks it's useful?"

This made me wonder why none of Java's standard queuing interfaces have implementations here. Is there a specific reason for that?

If this is need interesting I can submit a PR for the BlockingQueue and implementations of Queue as well.

[JakeWharton]

The main reason is that the queue is not safe for concurrent interaction. A quick glance at the BlockingQueue docs and your gist makes it seem like you are not fulfilling the contract of the interface:

BlockingQueue implementations are thread-safe.

[pschichtel]

All operations to the backing QueueFile are synchronized, so there is no concurrent access to the QueueFile (unless of course someone shares the QueueFile instances to other places). This is similar to the ArrayBlockingQueue which synchronizes every operation to the backing array.
I've missed the locking in the add() method, but that's fixed locally.

[JakeWharton]

Ah, haha. The add method was the only one I looked at!

I don't think I'm opposed to adding this if you're willing to send a PR and write tests.