Synchronization doubt

[Animesh Shrivastava]

I am not able to understand the concept of synchronization.
Look at this program:

---------------------------------------------------------------------------
public class Synch extends Thread{

public static void main(String[] args) {
Synch synch1 = new Synch();
synch1.start();
Synch synch2 = new Synch();
synch2.start();
Synch synch3 = new Synch();
synch3.start();
}

public synchronized void run() {
try {
for(int i = 0; i < 100; i ++) {
System.out.println("I am " + Thread.currentThread().getName() + " and this is my " + i + "th" +" time");
}
sleep(10000);
} catch(InterruptedException ie) {
System.out.println("I am interrupted");
}
}
}
--------------------------------------------------------------------------
As far as i know about Synchronization of methods, it says that, a single thread can only access the synchronized method and no other thread is allowed to access the method until the owner completes its execution. But here in the example i have shown above the ouput is something like

I am Thread-1 and this is my 0th time
I am Thread-1 and this is my 1th time
I am Thread-1 and this is my 2th time
I am Thread-1 and this is my 3th time
I am Thread-1 and this is my 4th time
I am Thread-0 and this is my 0th time
I am Thread-2 and this is my 0th time
I am Thread-2 and this is my 1th time
I am Thread-2 and this is my 2th time
I am Thread-2 and this is my 3th time
...........

Shouldn't the output be:
I am Thread-1 and this is my 0th time
I am Thread-1 and this is my 1th time
I am Thread-1 and this is my 2th time
I am Thread-1 and this is my 3th time
I am Thread-1 and this is my 4th time
I am Thread-1 and this is my 5th time
I am Thread-1 and this is my 6th time
I am Thread-1 and this is my 7th time
I am Thread-1 and this is my 8th time
....
...
I am Thread-1 and this is my 99th time
...
....
.....



Thanks

[ankur rathi]

No but in your case , every thread has its own synchronized code . It is not the case , one object has synchronized code & all the threads are trying to aquire the lock of this object .

hope it helps ...

[Animesh Shrivastava]

Ok then how do i acheive it in my code?
How can u say every thread has its own synchronized code?
please explain more about this?

[ankur rathi]

 
class Synch {
  public synchronized void run() {
    try {
      for(int i = 0; i < 100; i ++) {
System.out.println("I am " +  Thread.currentThread().getName() + " and this is my " + i + "th" +" time");
      }
    sleep(10000);
    } catch(InterruptedException ie) {
System.out.println("I am interrupted");
    }
  }
}
 
public class SynchTest extends Thread{
  public static void main(String[] args) {
    Synch syn = new Synch();
    SynchTest synTest1 = new SynchTest(syn);
    synTest1.start();
    SynchTest synTest2 = new SynchTest(syn);
    synTest2.start();
    SynchTest synTest3 = new SynchTest(syn);
    synTest3.start();
  }
}

I have not executed that program , but hope it is solving your purpose .
try & let me know ...
[ February 15, 2005: Message edited by: rathi ji ]

[Animesh Shrivastava]

According to ur code:

public class SynchTest extends Thread{
public static void main(String[] args) {
Synch syn = new Synch();
SynchTest synTest1 = new Synch(syn);
synTest1.start();
SynchTest synTest2 = new Synch(syn);
synTest2.start();
SynchTest synTest3 = new Synch(syn);
synTest3.start();
}
}

Ur code doesnt compile because u r using a new Synch(syn); and many such errors in other places.
anyways,
Well, i guess u must have meant by writing the method run in a different class and calling it from a different class.
But i tried that way too,
its not solving my purpose.

[ankur rathi]

Sorry Animesh , It was a mistake . But I have edited my code now .

[Subhash Bhushan C]

This thread should probably answer your questions.