Java – how to check how many threads are waiting for the synchronization method to unlock

Is there any way to check how many threads are waiting for the synchronization method to unlock?

I want to know when a thread calls a synchronized method:

1) How many threads are already waiting to call the method?

2) Once a method is called, how long does it take to wait for the method to unlock?

Solution: I solved this problem with stacker:

public class LockedClass {
    public static int count;
    public static void measuringClass() throws IOException{
        long startTime = System.currentTimeMillis();
        count++;
        System.out.println("Threads waiting="+count);
        lockedMethod(startTime);
        count--;
        System.out.println("Threads waiting="+count);
    }
    public static synchronized void lockedMethod(long startTime) throws IOException{
        System.out.println("I spent="+(System.currentTimeMillis()-startTime)+" in the queue");
        Hashtable<String,String> params = new Hashtable<String,String>();
        params.put("param1","test");
        params.put("param2","12345678");
        String sessionId = Common.getSession(Common.executeHttpRequest(params));
    }
}

Solution

You can convert code to use synchronous blocks instead of synchronous methods, which is my rough draft I don't know if it meets your second requirement (due to my broken English)

public class Sync {
    public static int waiting = 0;
    private Object mutex = new Object();

    public void sync() {
        waiting++;
        synchronized (mutex) {
            waiting--;
            long start = System.currentTimeMillis();
            doWhatever();
            System.out.println("duration:"
                    + (System.currentTimeMillis() - start));
        }
    }
}