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Calling methods before start()

 
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A/C to Sun Java2 Tutorial,


When a thread is in New Thread state, you can only start the thread. Calling any method besides start when a thread is in this state makes no sense and causes an IllegalThreadStateException.


Anybody can give code based e.g.?
Bye.
Viki.
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Valentin: correct this, if wrong...
We will get IllegalThreadStateException only in two cases.
1) When we call start() on already started thread
2) When we call setDaemon() after the thread is started
Uma
 
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Uma,
1. true
2. not exactly started but "active", but I think it's the same!
3. also when we invoke countStackFrames is the thread is not suspended, but don;t worry that method is deprecated...
HIH
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Valentin Crettaz
Sun Certified Programmer for Java 2 Platform
[This message has been edited by Valentin Crettaz (edited December 11, 2001).]
 
Uma Viswanathan
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Val: Thanks for your reply.
That exception will be thrown if we call setDaemon()when the thread is active...this is proper wording...
but I thought that a thread is active after it is started. That's why, i phrased the words like that.
OK. Can a thread be inactive, after it is started? If so, please explain val...
Is the thread inactive if it is waiting or blocking or suspended...?
Uma
 
Valentin Crettaz
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it depends on what you call an active thread:
Here is a quote from Java Threads (O'Reilly):


When is a Thread active? At first glance, this seems to be a simple question. Using the isAlive() method, a thread is considered alive during the period between the call to the start() method and a short time period after the stop() method is called. We might consider a threada ctive if it is alive.
However, if the definition of an active thread is a thread whose thread reference appears in the active count returned by the activeCount() method, we would have a different definition of active. A thread reference first appears in the thread array returned by the enumerate() method, and is counted by the activeCount() method, when the thread object is first constructed and not when the thread is started.
The thread is removed from the thread array either when the thread is stopped or when the run() method has completed. This means that if a thread object is constructed but is not started, the thread object will not be removed from the enumeration list, even if the original reference to the object is lost.


HIH
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Valentin Crettaz
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Uma Viswanathan
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setDaemon() throws that exception if called before a thread is started
Thread t = new Thread();
t.start();
t.setDeamon( true ); //throws exception
Thread t = new Thread();
t.setDaemon();
t.start(); //does not throw exception
Java API says that we need to call setDaemon() before the thread is started. Also it says that it will throw that exception if the thread is active.
According to the above code and API, a thread is active only when it is started (but not just being creating the Thread object)
So, the definition from Java Threads (O'Reilly) and also activeCount() method "contradicts with" JAVA API. i.e, If a thread is considered to be active as soon as it is constructed (even before it is started)...
 
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Vikrama Sanjeeva
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A thread reference first appears in the thread array returned by the enumerate() method, and is counted by the activeCount() method, when the thread object is first constructed and not when the thread is started.
This para of O'Reilly says that Thread is even active when before start() is call.But i think a/c to cert. we have to consider the active thread as said by this para of O'Reilly


When is a Thread active? At first glance, this seems to be a simple question.Using the isAlive() method, a thread is considered alive during the period between the call to the start() method and a short time period after the stop() method is called.


A/C to me this para defines the correct state of Thread a/c to cert. point of view.
Bye.
Viki.

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Uma Viswanathan
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Thanks Marilyn.
It clears my doubt (I think)...
So, the O'Reilly explanation is correct...
1) A thread is alive between the call to the start() method and a short time period after the stop() method is called.
2) A thread is active between the period (when the thread object is first constructed and not when the thread is started) and (either when the thread is stopped or when the run() method has
completed).
Need a change in the API for setDaemon():
They should specify this method will throw the exception if called when a thread is alive. THEY SHOULD NOT TELL THAT THIS EXCPETION WILL BE THROWN WHEN THE THREAD IS ACTIVE...YOUR CODE CONFIRMS THIS...
 
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Thread Boost feature
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