Question

I was using an ExecutorService to schedule tasks to be executed in future. After seeing some “odd” behavior where my Callable was getting executed before I called get() on the Future object returned by submitting my Callable to the ExecutorService pool, I read some documentation and found that the submitted task will get executed between the time it gets submitted or at the latest when get() is called on the Future object.

My question – is there any class that would allow Callables to be submitted to it and ONLY executed when get() is called on it? At this point, it seems like just managing the Callables myself and calling call() on them myself when I am ready for them to be executed seems like it’d accomplish what I want, but I wanted to make sure there was no service already implemented that accomplished this.

In short, is there any alternative to ExecutorService that lets me control when Callables submitted to it are called? Note – the time in the future that I want them called is variable and not determined as I may decide not to call them so a ScheduledExecutorService pool won’t work here.

Thanks much!

Answer 1

Sounds like you really want to use a Queue<Callable> instead and just poll the queue for tasks.

That way you can submit as many tasks as you like and execute them at your will – one by one.