Thread - The # between static synchronized and non static synchronized

[Reda Mokrane]

hi all,
what's the difference of these static synchronized and non static synchronized?
why the output is # ?
here is the code for the static synchronized

class SyncStatic extends Thread {
  SyncStatic(String name) {
    setName(name);
  }
  public void run() {
    myMethod(getName());
  }
  static synchronized public void myMethod(String name) {
    for(int i=0; i<5; i++) {
      System.out.println(name+"\t("+i+")");
    }
  }
  public static void main(String args[]) {
    SyncStatic t1 = new SyncStatic("t1");
    SyncStatic t2 = new SyncStatic("t2");
    t1.start();
    t2.start();
  }

}
/*
output
t1      (0)
t1      (1)
t1      (2)
t1      (3)
t1      (4)
t2      (0)
t2      (1)
t2      (2)
t2      (3)
t2      (4)
*/

here is the code for the non static

class SyncNoStatic extends Thread {
  SyncNoStatic(String name) {
    setName(name);
  }
  public void run() {
    myMethod(getName());
  }
  synchronized public void myMethod(String name) {
    for(int i=0; i<5; i++) {
      System.out.println(name+"\t("+i+")");
    }
  }
  public static void main(String args[]) {
    SyncNoStatic t1 = new SyncNoStatic("t1");
    SyncNoStatic t2 = new SyncNoStatic("t2");
    t1.start();
    t2.start();
  }

}
/*
t1      (0)
t2      (0)
t1      (1)
t2      (1)
t1      (2)
t2      (2)
t1      (3)
t2      (3)
t1      (4)
t2      (4)
*/

[Alex Sbityakov]

I think the difference is that, the first code defines a class lock. So, when you instantiate two objects of the same class, the second string must wait for the first to finish, since it is unable to access the class lock.
In the second example, you have object locks. Since you have two different objects, nothing prevents the two threads fom running concurrently.
Correct me if I'm wrong,
Alex

[Reda Mokrane]

object locks and class locks...
thank you Alex.

[MrShahid khan]

Alex is right
u cannot execute non-static synchronized methods simultaneouly for the same object
whereas for the static sync methods since they are assoiciated with the class they cannot be executed for the class simultaneoulsy

[Reda Mokrane]

For a static method, a " lock " is obtained for the class before the execution of the method.
Correct me if I'm wrong.

[Ragu Sivaraman]

Before entering the synch code, the thread should have the
object or class lock. Thats how semaphores work (monitors in java)
HTH

[Rashmi Hosalli]

Alex,
Can two threads run concurrently?
and MrShahid khan,can you please explain more clearly...I am a bit confused here.
Thanks,
Rashmi