How to request monitor info on/from a locked object

[Ronald Vermeij]

Hello Java Guru's
Scenario: The Classic Producer - Cubbyhole - Consumer example from Sun Microsystems

public class ProducerConsumerTest {
    public static void main(String[] args) {
        CubbyHole c = new CubbyHole();
        Producer p1 = new Producer(c, 1);
        Consumer c1 = new Consumer(c, 1);
        p1.start();
        c1.start();
    }
}

class CubbyHole {
    private int contents;
    private boolean available = false;

    public synchronized int get() {
        while (available == false) {
            try {
                wait();
            } catch (InterruptedException e) { }
        }
        available = false;
        notifyAll();
        return contents;
    }

    public synchronized void put(int value) {
        while (available == true) {
            try {
                wait();
            } catch (InterruptedException e) { }
        }
        contents = value;
        available = true;
        notifyAll();
    }
}


class Consumer extends Thread {
    private CubbyHole cubbyhole;
    private int number;

    public Consumer(CubbyHole c, int number) {
        cubbyhole = c;
        this.number = number;
    }

    public void run() {
        int value = 0;
        for (int i = 0; i < 10; i++) {
            value = cubbyhole.get();
            System.out.println("Consumer #" + this.number
                               + " got: " + value);
        }
    }
}

class Producer extends Thread {
    private CubbyHole cubbyhole;
    private int number;

    public Producer(CubbyHole c, int number) {
        cubbyhole = c;
        this.number = number;
    }

    public void run() {
        for (int i = 0; i < 10; i++) {
            cubbyhole.put(i);
            System.out.println("Producer #" + this.number
                               + " put: " + i);
            try {
                sleep((int)(Math.random() * 100));
            } catch (InterruptedException e) { }
        }
    }
}

My challenge
I'm writing a "third thread" called "monitor_status".
Via this 3rd thread I want to
- get information out of the (java object) monitor that guards the Cubyhole object.
- to monitor the Thread.status of both the Producer and the Consumer threads.

Via the Thread. getState() Is can see in which status a thread is [new],[runnable][,...], etc...
I have not discovered any "java.lang.Object" Class method that provides access to monitor/lock information.


Question:
1. Is it possible (with the example above) to get information on the status of the monitor / lock on the Cubyhole object?
2. Is it possible to look into the monitors ENTER_queue and WAIT_queue? (to see which calling thread are in which monitor_queue)
or...
3. Do i have to rewrite this example to make use of the "java.util.concurrent.locks" Lock object instead of wait(), notify() methods?


I do have found the java.lang.management.MonitorInfo Class, but i can not find a good example that shows me how to use it.
4. Do you have an code-example on how to use this class?

Thanks for sharing your insight on this java monitor / object lock matter.