Question

So let’s say I’m creating and starting a bunch of threads in a for loop, that is being executed in the run method of a launcher thread. Let’s also say that I want to be able to interrupt the launcher thread and all threads that the thread has created, and I do this through a button.

So something like this –

try{
            for(int i = 0; i < n;i++){

                Worker currThread = new Worker(someArgs);
                workerThreads.add(currThread);
                currThread.start();
            }
        } catch (InterruptedException e){
            e.printStackTrace();
        }

BUTTON-

public void actionPerformed(ActionEvent arg0) {

    List<Worker> threads = launchThread.getWorkerThreads();
        for(int i = 0; i < threads.size();i++){
            threads.get(i).interrupt();
        }
        launchThread.interrupt();

    }

Now, let’s say that I want to make it so that the interrupts cannot occur at the same time as thread creation. I think a way to do this would be to construct a dummy object and put both pieces of code inside a lock

synchronized(dummyObject){
//thread creation or interruption code here (shown above) 
}

Will this way work? I ask because I’m not sure how to test to see if it will.

Answer 1

Start the threads separately from creating them.

for(int i = 0; i < n; i++) {
    Worker currThread = new Worker(someArgs);
    workerThreads.add(currThread);
}

// later
for (Worker w : workerThreads) {
    w.start();
}

If that’s still not enough, your dummyObject synchronization should work just fine.

// You probably need to make this a (private final) field
Object lock = new Object();

// later
synchronized (lock) {
    for(int i = 0; i < n; i++) {
        Worker currThread = new Worker(someArgs);
        workerThreads.add(currThread);
        w.start();
    }
}

// later still
public void actionPerformed(ActionEvent arg0) {
    synchronized (lock) {
        // interruption code here
    }
}