K&B Threads: subtle detail calling start() important?

[Gian Franco]

Hi,

In K&B Chapter 9 on threads is says:

Dead A thread is considered dead when its run()
method completes. It may still be a viable Thread object, but
it is no longer a separate thread of execution. Once a thread
is dead, it can never be brought back to life! (The whole "I
see dead threads" thing.) If you invoke start() on a dead Thread
instance, you�ll get a runtime (not compiler) exception.

The following code does not give me an java.lang.IllegalThreadStateException

public class JTC26 implements Runnable{
public void run(){
System.out.println("JTC26 running.");
}
public static void main(String[] args){
JTC26 j = new JTC26();
Thread t = new Thread(j);
t.start();
try{
t.join();
System.out.println("main 1");
Thread.sleep(10000);
}
catch(InterruptedException e){
}
t.start();
System.out.println("main 2");
}
}

it compiles and runs fine.

The answer to this is (from "Java Threads, 2nd Edition" by S. Oaks
and H. Wong, Chapter 2.6)

What happens when you try to restart a thread? The answer is
that it actually depends on when you restart it
...
it actually takes time for a thread to stop.
...
If the start() method is called after the stopping thread has actually
stopped, nothing happens: the thread object is in a state where it
cannot be restarted

Can an exam question go into such low level details?

Cheers,

Gian Franco
[ May 20, 2004: Message edited by: Gian Franco Casula ]

[Barry Gaunt]

Did you read this thread?

And from the books errata:

Page 505,Second paragraph2/07/03

Change:
.. method has finished, you can't say t.start(); you'll get a big fat runtime exception.
To:
.. method has finished, calling t.start() won't restart it.

The errata is here.
[ May 20, 2004: Message edited by: Barry Gaunt ]

[Gian Franco]

Thanks Barry, I didn't see that topic-thread before.

Cheers,

Gian Franco