Concurrent access to a static variable

Question

I think that I need a static lock to protect a static variable. However, the code below seems to be running fine on a 24-CPU machine.
public class test {
public static void main(String[] args)
  new Thread(new myclass()).start();
  new Thread(new myclass()).start();
class myclass implements Runnable {
private static int msgid;
private Object lock = new Object();
public void run()
   synchronized(lock) {
   int i=200000;
   while(i-- >0) {
   msgid = msgid+1;
   System.out.println("Thread " + Thread.currentThread().getName() + "value => "
+ msgid);
}This testcode is roughly based on my actual program. I have a code (written by someone else) which protects the static msgid with an instance-level lock. IMHO , this shouldn't stop the multithreaded access to the msgId because two threads will have two different instances of the lock. However, I can't reproduce this on a 24-CPU machine. I know the MT-related bugs are hard to reproduce. So I just thought of confirming it with the experts. In my opinion, lock object should be :
private static Object lock = new Object();
Anyone against this thought?

Answer 1

Yes I see the code and I can see the "msgid" can be updated by both threads randomly behaved as per CPU time slicing for each thread.
like ThreadOne msgId-->10
ThreadTwo msgId-->11
ThreadTwo msgId--->12
ThreadOne msgId -->13
etc..
What do you want to achieve if you use a common resource to lock in order to prevent the msgId to be incremented by two thread at the same time but rather by one thread at a time?
Regards,
Alan Mehio