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javamultithreadingconcurrencyscheduled-tasksscheduling
Mike Howard
Mike Howard

Reputation: 53

Thread Scheduling - Run threads in set order

I have a set of roughly 20 threads and i want to schedule them so they run in a set order. Is there a way to do this. I have tried using priority and setting the priority 1-10 but the scheduler still seems to execute threads at its own order. Btw im working in Java

Is there a way to run threads in a set order ?

Thanks regards Mike

Upvotes: 0

Views: 1528

Answers (4)

shams
shams

Reputation: 3508

You don't have to run a single threaded version if the jobs can be executed in parallel. Below is an example where you can use eight threads to run your 20 jobs:

public static void main(String[] args) {
    final ExecutorService executorService = Executors.newFixedThreadPool(8);
    final Queue<Integer> workItems = new ConcurrentLinkedQueue<Integer>();
    for (int i = 0; i < 20; i++) {
        workItems.add(i);
    }
    for (int i = 0; i < 20; i++) {
        executorService.submit(new Runnable() {
            @Override
            public void run() {
                final Integer workIem = workItems.poll();
                // process work item
            }
        });
    }
    // await termination of the exec service using shutdown() and awaitTermination()

}

The idea is that you use an auxiliary queue to maintain the items to be processed and rely on the FIFO ordering of the queue to process the items in order and in parallel.

Upvotes: 1

mprivat
mprivat

Reputation: 21902

If the threads depend on each other, then one option would be to schedule only the first thread and have it spawn its dependent threads, which can then turn their dependent threads, etc...

You need to understand, however, that even though you may be launching threads in a particular order, as soon as they start they are off of your hands and they will be fighting for resources and the OS will time-slice their executions, which means some may get "ahead" of threads that were launched before. So if you truly need to keep the order, then I would suggest you use only one thread and let it orchestrate the tasks in a synchronized manner.

Upvotes: 0

Snicolas
Snicolas

Reputation: 38168

What you need is an ExecutorService that will run your threads one at a time, namely : newSingleThreadExecutor.

 ExecutorService pool = Executors.newSingleThreadExecutor(); 
 pool.submit(job1);
 pool.submit(job2);
 pool.submit(job3);

Upvotes: 2

Clive Evans
Clive Evans

Reputation: 658

Why do you have multiple threads if you want synchronous behaviour in the first place?

If you've acquired multiple Thread objects from "something else" then you can use thread.run() to execute them in the current thread, which will, of course allow you to control the order.

Upvotes: 1

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