Question

I have a main process main. It creates 10 threads (say) and then what i want to do is the following:

while(required){
Thread t= new Thread(new ClassImplementingRunnable());
t.start();
counter++;
}

Now i have the list of these threads, and for each thread i want to do a set of process, same for all, hence i put that implementation in the run method of ClassImplementingRunnable.

Now after the threads have done their execution, i wan to wait for all of them to stop, and then evoke them again, but this time i want to do them serially not in parallel.

for this I join each thread, to wait for them to finish execution but after that i am not sure how to evoke them again and run that piece of code serially.
Can i do something like

for(each thread){
t.reevoke(); //how can i do that.
t.doThis();  // Also where does `dothis()` go, given that my ClassImplementingRunnable is an inner class.
}

Also, i want to use the same thread, i.e. i want the to continue from where they left off, but in a serial manner.
I am not sure how to go about the last piece of pseudo code.
Kindly help.
Working with with java.

Answer 1

You can’t restart a thread.

What you could do is use the java.util.concurrent package to wait for the threads to finish and rerun you runnables in the main thread to run them sequentially – by putting your runnables in a list, you can access them during the sequential run.

ExecutorService executor = Executors.newFixedThreadPool(10);
List<Runnable> runnables = new ArrayList<Runnable> ();

for (int i = 0; i < 10; i++) {
    Runnable r = new ClassImplementingRunnable();
    runnables.add(r);
    executor.submit(r);
}

executor.shutdown();
//wait until all tasks are finished
executor.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);

//re run the tasks sequentially
for (ClassImplementingRunnable r : runnables) {
    //the method below can access some variable in 
    //your ClassImplementingRunnable object, that was 
    //set during the first parallel run
    r.doSomethingElse(); 
}