Controlling Task execution order with ExecutorService

Question

I have a process which delegates asynch tasks to a pool of threads. I need to ensure that certain tasks are executed in order. So for example

Tasks arrive in order<

Answer 1

I have written my won executor service which is sequence aware. It sequences the tasks which contain certain related reference and currently inflight.

You can go through the implementation at https://github.com/nenapu/SequenceAwareExecutorService