Sample code to test an object monitor

package com.pierre;

public class LockGeneration {
 public static Object myMonitor = new Object();

 public static void main(String[] args) throws InterruptedException {
  T1 t1 = new T1();
  T2 t2 = new T2();
  t1.start();
  t2.start();
  for (;;) {
   Thread.sleep(1000);
  }
 }

}

class T1 extends Thread {

 @Override
 public void run() {
  System.out.println("T1 started");
  super.run();
  for (;;) {
   try {
    synchronized (LockGeneration.myMonitor) {
     Thread.sleep(1030);
    }
    Thread.sleep(10);
   } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  }
 }

}

class T2 extends Thread {

 @Override
 public void run() {
  System.out.println("T2 started");
  super.run();
  for (;;) {
   try {
    synchronized (LockGeneration.myMonitor) {
     Thread.sleep(1050);
    }
    Thread.sleep(10);
   } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  }
 }

}

a thread dump will show for instance:

"Thread-1" prio=6 tid=0x000000001b9be000 nid=0x3c4c waiting for monitor entry [0x000000001c57f000]
   java.lang.Thread.State: BLOCKED (on object monitor)
 at com.pierre.T2.run(LockGeneration.java:48)
 - waiting to lock <0x0000000755ecf6b0> (a java.lang.Object)

   Locked ownable synchronizers:
 - None

"Thread-0" prio=6 tid=0x000000001b9bd000 nid=0x513c waiting on condition [0x000000001c47f000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
 at java.lang.Thread.sleep(Native Method)
 at com.pierre.T1.run(LockGeneration.java:27)
 - locked <0x0000000755ecf6b0> (a java.lang.Object)

   Locked ownable synchronizers:
 - None

so the thread (T1 in this case) holding the lock on the object monitor will show "locked < OBJECT ID > " (the TD shows also the TYPE of the lock, a java.lang.Object)

the thread T1 when sleeping will be in TIMED_WAITING (= wait for on a notification but with a timeout), and waiting on condition

the thread T2 waiting to acquire the lock will be in BLOCKED (on object monitor) and waiting to lock <0x0000000755ecf6b0> (which is the same OBJECT ID held by T1.