Evidence 4 Main Thread dead after main method exits

Hi all,
I read Maha's discussions, I found her discussions is really useful and great, but in the Threads topic i found her saying that Main thread will wait till all its child threads dies . But the program given below shows clearly contradicts, may be i'm wrong, so i want comments on this as i'm taking the SCJP2 within 2 weeks.

public class AfterAllThreadProgram extends Thread
{
static Thread t1;

public void run()
{
System.out.println("Thread Group Name is " + Thread.currentThread().getThreadGroup());
while(true)
{
System.out.println("Child Thread " + Thread.currentThread().getName());
System.out.println(t1.isAlive());//Prints first true indicating main is alive. This will
//continue atleast 1 sec. After that it prints false
//This means that main thread is dead.
System.out.println("Total Threads  " + Thread.currentThread().activeCount());
//Here the activecount always prints 2 Why??? It is suppose to be 1 as per my knowledge

}
}

public static void main(String args[]) throws InterruptedException
{
System.out.println(Thread.currentThread().getName()+ " is the Main Thread & started executing");
System.out.println("Thread Group Name is " + Thread.currentThread().getThreadGroup());

System.out.println("Total Threads in this ThreadGroup is " + Thread.currentThread().activeCount());
//Here it is printing 1 and it is correct since only main thread is alive

t1 = Thread.currentThread();

Thread t = new AfterAllThreadProgram();
System.out.println("Total Threads in this ThreadGroup is " + Thread.currentThread().activeCount());
//Here it is printing 2  even before starting child thread, why???
//my surprise is whether child thread is active even before starting it.

t.start();

sleep(1000);

System.out.println("Main Method terminated");
}
}

with regards,
Jeganathan

Main thread does not wait for all children threads. Main thread by default is a daemon thread.

Adrian,
Main thread is not a daemon thread, it is a user thread. The main ThradGroup is not daemon either.
Take a look at the following code( and read the comments ) which proves my point.

/*
Logic - 
When code running in some thread creates a new Thread object, 
the new thread has its priority initially set equal to the 
priority of the creating thread, and is a 
daemon thread if and only if the creating thread is a daemon. 
*/
public class IsMainDaemon
{
    public static void main( String[] s)
    {
        // Create a new thread object. This thread now belongs
        // to the same ThreadGroup as the main thread and hence
        // inherits the properities such as priority and daemon-ness
        Thread t = new Thread() ;
                
        // This line will affirm that this new thread and the main
        // thread belongs to the same ThreadGroup ie., "main"
        System.out.println( t.getThreadGroup());
        
        // Is the thread group of the new thread daemon?
        // Remember main belongs to the same thread group too!
        System.out.println( t.getThreadGroup().isDaemon());
    
        // Is the new thread itself daemon??
        // This affirms that the new thread really inherits the 
        // daemon-ness from the parent ThreadGroup/Thread. Since we
        // have no explicitly set the new thread as daemon, the following
        // line should return false.
        System.out.println( t.isDaemon());
    
    }
}

Hope that helps,
Ajith

I agree that main thread is not a Daemon thread but can anyone comment about Whether main thread exits when main method terminates? And thanks a lot 4 ur replies.

Yes Jeganathan main thread dies before the child thread in your case. I too had this confusion but after reading khalid I'm satisfied. Read page no. 273.
My doubt originated from the program that I tried. Here's it.
// program to demonstrate main thread dies before the child thread.
class ChildThread extends Thread
{
Thread mainThread;
ChildThread(Thread t)
{
mainThread = t;
}
public void run()
{
System.out.println("Main thread is alive at the start of run meth() : " + mainThread.isAlive());
try
{
for(int i =0;i<5;i++)
{
sleep(500);
System.out.println("Child Thread counting : " + i);
System.out.println("Main thread is alive in the run meth() : " + mainThread.isAlive());
}
} catch(InterruptedException r){}
System.out.println("Main thread is alive at the end of run meth() : " + mainThread.isAlive());
}
}
public class MainThreadIsAlive
{
public static void main(String a[])
{
Thread t = Thread.currentThread();
System.out.println("Main thread is alive at the start of main meth() : " + t.isAlive());
ChildThread child = new ChildThread(t);
child.start();
System.out.println("Main thread is alive at the end of main meth() : " + t.isAlive());
}
}
-vadiraj