Question

I am working on a project in which I need to make sure each thread get’s unique ID every time in a particular range. For example-

If number of threads is 2 and number of tasks is 10 then each thread will be performing 10 tasks. So that means 2 thread will be doing 20 tasks.

So what I am looking for something like this-

In the above example, first thread should be using id between 1 and 10 and second thread should be using id between 11 and 20.

Another example. So suppose if I have 3 thread and number of tasks as 20 then first thread should be using ID between 1 and 20 and second thread should be between 21 and 40 and third thread in between 41 and 60.

Below is the code I have so far, what it does is that it will get id as an AtomicInteger and I am getting unique id every time starting from 1.

class ThreadTask implements Runnable {
    private final AtomicInteger id;
    private int noOfTasks;

    public ThreadTask(AtomicInteger id2, int noOfTasks) {
        this.id = id2;
        this.noOfTasks = noOfTasks;
    }

    @Override
    public void run() {

        while(noOfTasks > 0) {
            System.out.println(id.getAndIncrement());
              // And use this id for other things.
        noOfTasks--;
         }
    }
}

public class XMPTest {

    public static void main(String[] args) {

        final int noOfThreads = 2;
        final int noOfTasks = 10;

        final AtomicInteger id = new AtomicInteger(1);

        //create thread pool with given size 
        ExecutorService service = Executors.newFixedThreadPool(noOfThreads);

        // queue some tasks 
        for (int i = 0; i < noOfThreads; i++) {
            service.submit(new ThreadTask(id, noOfTasks));
        }
    }
}

How can I restrict this such that thread 1 should get id between 1 and 10 and second thread should get id between 11 and 20

Updated Code:-
I am trying the below code

public static void main(String[] args) {

    final int noOfThreads = 2;
    final int noOfTasks = 10;

    //create thread pool with given size 
    ExecutorService service = Executors.newFixedThreadPool(noOfThreads);

    // queue some tasks 
    for (int i = 0, int nextId = 1; i < noOfThreads; i++, nextId += noOfTasks) {
        service.submit(new ThreadTask(nextId, noOfTasks));
    }
}


class ThreadTask implements Runnable {
    private final int id;
    private int noOfTasks;

    public ThreadTask(int nextId, int noOfTasks) {
        this.id = nextId;
        this.noOfTasks = noOfTasks;
    }

    public void run() {

        for (int i = id; i <= noOfTasks; i++) {
            System.out.println(i);
        }
    }
}

So for the first thread it is printing out 1 – 10 which is fine. But in the second thread, nextId is 11 and noOfTasks is 10 so my for loop going to work in the run method for second time.

Answer 1

Split up the range however you want in the singlethreaded code before you launch your threads, then pass the range to each thread.

For example:

public static void main(String[] args) {

    final int noOfThreads = 2;
    final int noOfTasks = 10;

    //create thread pool with given size 
    ExecutorService service = Executors.newFixedThreadPool(noOfThreads);

    // queue some tasks 
    for (int i = 0, int nextId = 1; i < noOfThreads; i++, nextId += noOfTasks) {
        service.submit(new ThreadTask(nextId, noOfTasks));
    }
}

class ThreadTask implements Runnable {
    private final int id;
    private int noOfTasks;

    public ThreadTask(int nextId, int noOfTasks) {
        this.id = nextId;
        this.noOfTasks = noOfTasks;
    }

    public void run() {

        for (int i = id; i < id + noOfTasks; i++) {
            System.out.println(i);
        }
    }
}