How to change a thread's Runnable target during runtime

Patrick :

I want to build my own ExecutorService in Java which is able to 'submit(Callable task)' a given task. I intended to use a thread pool comprising several 'Threads(Runnable target)'. The idea is to create a fixed number of threads which dequeue FutureTask objects from a list that has been filled by the 'submit' method. The FutureTask objects have been created within the submit method as well. My problem is that I can only hand over a Runnable object(here: FutureTask) to a thread when the thread is created (via constructor), but obviously FutureTasks need to be assigned to a thread dynamically (when the item is removed from the list). Is there any way to do this?

// content of submit, parameter: myTask
FutureTask<V> newFutureTask = new FutureTask<V>(myTask);
taskQueue = new BlockingQueue<FutureTask<V>>();
try {
    taskQueue.put(newFutureTask);
} catch (InterruptedException ex) { }
return newFutureTask;

// remove item from list and hand it over to thread
// method within MyThread extends Thread (thread pool) class
void exec() {
    FutureTask<V> task;
    try {
        task = taskQueue.take();
        // TODO: run task somehow????
        } catch(InterruptedException ex) { }
}

GhostCat salutes Monica C. :

See a bit of pseudo code:

while (true) {
   task = fetch task
   If no task: wait/yield
   Else: execute task 
}

In other words: you simply have to implement a run() method that loops and executes the run method of any Runnable (or whatever is passed to it). If no work is available, that methods sleeps, or waits to be notified.