Threads Question

[Hussain]

hi all,
the following program compile but hangon at runtime
public class G124 extends Thread
{
G124 a=new G124();
public void run()
{
a.a();
}
public synchronized void a()
{
int i=0;
while(i++<3)
System.out.println("A "+i);
}
public static void main(String [] args)
{
G124 a=new G124();a.start();
G124 b=new G124();b.start();
}
}
------------------
Muhammad Hussain

[Marilyn de Queiroz]

<font size=2>public class G124 extends Thread
{
    G124 a = new G124();  // Line 1
    public void run()
    {
        a.a();
    }
    
    public synchronized void a()
    {
        int i = 0;
        while( i++ < 3 )
    }
    
    public static void main( String[] args )
    {
        G124 a = new G124(); // Line 2
        a.start();
        G124 b = new G124();
        b.start();
    }
}

When you create a new instance of G124 in Line 2, it causes the creation of a new instance of the instance variable in Line 1, which causes the creation of a new instance of the instance variable in Line 1, which causes the creation of a new instance of the instance variable in Line 1, which causes the creation of a new instance of the instance variable in Line 1, ...

[Hussain]

thankx Marilyn deQueiroz

i got it..........
actually i m making this more simple
that is
at Line 1 the Object creates another G129 Object and another..................................................................................another........................................
------------------
Muhammad Hussain

[farrukh mahmud]

Hi Marilyn deQueiroz
can u plz explain it because i am unable to grasp it or any other java Guru
Thanks

------------------
Regards
Farrukh Mahmud

[Andre Zhang]

Let's make the code simple first.
public class G124 extends Thread
{
G124 a = new G124();
public static void main(String[] args)
{
G124 a = new G124();
}
}
it will causes a hang-on at runtime because the unstoppable creation the a.
change this code a little more at the class declaration.
public class G124
{
G124 a = new G124();
public static void main(String[] args)
{
G124 a = new G124();
}
}
it causes a runtime error -- java.lang.StackOverflowError
my Question is: what's the difference between the two & why?

[Mathew Kuruvilla]

Hmmm! Nobody seems to have an answer for Andre's question. . . . My guess is that when creating instances of Thread subclasses, the JVM doesn't use the stack to create the instance, but uses the heap instead. On the other hand, for non-thread objects, the JVM uses the stack to hold some values. Therefore when the recursive creation of instances occurs, for Thread extended objects, it keeps going till some resource is exhausted (RAM, I think). For non-Thread objects, the stack overflow condition occurs earlier because the size of the stack is (???) is smaller than the amount of RAM available.
Bartender, we need a strong cup of Java here. :-)