Ensuring task execution order in threadpool

Question

I have been reading about the thread-pool pattern and I can\'t seem to find the usual solution for the following problem.

I sometimes want tasks to be executed serial

Answer 1

There is a java framework specifically for this purpose called dexecutor (disclaimer: I am the owner)

DefaultDependentTasksExecutor executor = newTaskExecutor();

    executor.addDependency("task1", "task2");
    executor.addDependency("task4", "task6");
    executor.addDependency("task6", "task8");

    executor.addIndependent("task3");
    executor.addIndependent("task5");
    executor.addIndependent("task7");

    executor.execute(ExecutionBehavior.RETRY_ONCE_TERMINATING);

task1, task3, task5,task7 runs in parallel (Depending upon thread pool size), once task1 finishes, task2 runs, once task2 finishes task4 runs, once task4 finishes task6 runs and finally once task6 finishes task8 runs.