How to access a Runnable object by Thread?

Question

Possible duplicate: need-help-returning-object-in-thread-run-method

Hello. I have a class implementing runnable and I have a List, storing Threads instantiated with

Answer 1

I had the same problem. Here is my solution:

public static class TestRunnable implements Runnable {
    public String foo = "hello";

    public void run() {
        foo = "world";
    }

public static void main(String[] args) {
    TestRunnable runobject = new TestRunnable();
    Thread t = new Thread(runobject);
    runobject.foo;  //The variable from runnable. hello;
    t.start();
    runobject.foo;  //The variable from runnable. world;
}

Answer 2

To give a concrete example of Paul Crowley's solution, I think this is what he suggests:

public class BackgroundJob<JOB extends Runnable> extends Thread {

    private final JOB mJob;

    public BackgroundJob(JOB job) {
        super(job);
        mJob = job;
    }

    public JOB getJob() {
        return mJob;
    }

}

Answer 3

This is how you could implement this directly.

public static void main(String[] args) {
    // Keep a reference to the runnable object for later ...
    TestRunnable r = new TestRunnable();
    Thread t = new Thread(r);
    t.start();
    // Wait until the child thread has finished
    t.join();
    // Pull the result out of the runnable.
    System.out.println(r.foo);
}

However, the modern (less error prone) way to do this kind of thing is to use the higher-level concurrency classes in java.util.concurrent.

Answer 4

I think, if you can, it is to revert the situation. Then in this case a good solution is to store the thread in your runnable class. And your runnable has a start() function that launch and start itself the local thread and call thread.start. Like this you can have a list of your threaded objects. Also you can have an accessor to get the thread.

public class Threaded extends other implements Runnable {
    Thread localThread;

    @Override
    public void run() {
        //...
    }

    public void start() {
        localThread = new Thread(this);
        localThread.start();
    }

}

Answer 5

TestRunnable r = new TestRunnable();
Thread t = new Thread(r);
t.start();
//there you need to wait until thread is finished, or just a simple Thread.sleep(1000); at this case
System.out.println(r.foo);

BTW, in real case you need to use Callable and FutureTask