Creating a queue that operates a job

I want to build a thread listens a queue and perform a job whenever i add a item to queue.

But i don’t much idea about how to develop it. I have already tried some Flowable examples from RxJava2 but not recognized how to do it.

I am open for all examples in Android and Java, Maybe message handler or executors would be an easy solution. Sadly no know-how. Esspecally RxJava2 would be great.