How can I avoid that each Thread creates a different pool?

Question

In my program I have a class called "Vehicle" which extends from Thread, the thing is that at a certain point I need these Threads to create a Task (Runnable) and I want all these tasks to be managed by the same Threadpool, the problem is that if I call a method from a different class that contains this Pool, every other thread is creating a different pool. How can I avoid this? Thanks in advance.

public class Station {
    Arrivals arrivals;
    Vehicle k;
    ListPumps lp;

    ExecutorService executor = Executors.newFixedThreadPool(3);
    public synchronized void startWork(Pump p) {

        Runnable w = new Work(p);
        executor.execute(w);

        executor.shutdown();
        while (!executor.isTerminated()) {
    }
        System.out.println("Finished all threads");
     }
}

Answer 1

Your code already uses a single threadpool. However if your class might have several instances and you want those to all share the same threadpool then assign it as a static variable.

Though I would also pull out the shutdown code to its own method too now. Also don't poll isTerminated, use awaitTermination.

Something like the following:

public class Station {

    private Arrivals arrivals;
    private Vehicle k;
    private ListPumps lp;

    private static ExecutorService executor = Executors.newFixedThreadPool(3);

    public void startWork(Pump p) {
        Runnable w = new Work(p);
        executor.execute(w);
    }

    public static synchronized void shutdown() {
        executor.shutdown();
        if(executor.awaitTermination(60, TimeUnit.SECONDS))
            System.out.println("Finished all threads");
        else
            System.out.println("Executor shutdown timed out");
    }
}