wait() and notifyAll()

[John Green]

I wanted to wake up t1 thread in t2 thread.
So I put notifyAll() in run() method of T2.
But it doesn't work.
No "t1 woke up" message. It just repeats "t2 run start"
What should I do?

class T1 extends Thread
{
public synchronized void run()
{
while(true){
System.out.println("t1 run start");
try {
System.out.println("t1 wait");
wait();
} 
catch(InterruptedException e) { }
System.out.println("t1 woke up");
}
}

public static void main(String[] args) 
{
T1 t1 = new T1();
t1.start();
T2 t2 = new T2();
t2.start();
System.out.println("hmm");
}
}
class T2 extends Thread
{
public synchronized void run()
{
while(true){
System.out.println("t2 run start");
try {
sleep(500);
} 
catch(InterruptedException e) { }
notifyAll();
}
}
}

[ May 27, 2003: Message edited by: John Green ]

[Saket Barve]

The way to do it is to create T1 object in class T2, and start it from there.
Next, you'll have to call t1.interrput() from t2 in order to evoke the InterruptedException. Realize that notifyAll() will work only if the object from which you are calling it is the owner of that object.

[Mr. C Lamont Gilbert]

The first thing you should know is that the documentation on the commands is VERY good. So look in the documentation to understand wait and notify.
notifyAll() is the same as this.notifyAll(); Which means it will notify anyone waiting on "this" object. you are calling this.wait() on the t1 object, but calling this.notifyAll() on the t2 object. you must make the calls on the same objects to get what you are looking for.

[Geoffrey Ren]

class T3
{
public static void main(String[] args)
{
T2 t2 = new T2();
t2.start();
System.out.println("hmm");
}
}
public class T1 extends Thread
{
public synchronized void run()
{
while(true)
{
System.out.println("t1 run start");
try
{
System.out.println("t1 wait");
wait();
}
catch(InterruptedException e)
{
System.out.println("e");
}
System.out.println("t1 woke up..............");
}
}

}
class T2 extends Thread
{
T1 t1;

public synchronized void run()
{
t1 = null;
while(true)
{
System.out.println("t2 run start");
try
{
t1 = new T1();
t1.start();

sleep(500);
}
catch(InterruptedException e)
{
}
System.out.println("invoke the t1 thread!!");
synchronized(t1)
{
t1.notifyAll();
}

}
}
}