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Thread Question

 
Greenhorn
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Hallo there,

Quick question.

Can anyone explain why the code below would work (apologies if you've seen this before).

class MyThread extends Thread {

publis static void main (String [] args)
MyThread t = new MyThread();
Thread x = new Thread(t); //I expect this line to throw a compiler error
x.start(); //
}
....

The constructor above takea s a thread object as an argument which is not valid. Am I missing something?

Appreciate any pointers ....
 
Ranch Hand
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Hi,
Please check thread constructors in Thread API. You will get the answer.Thread API
Check the above link.
 
Ranch Hand
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java.lang.Thread class implements java.lang.Runnable interface
Again, by extending the above Thread class, your MyThread class too is implementing Runnable interface!
Thread class' constructors allow you to pass a Runnable object typically called "target". In this case, your MyThread object referenced by 't' is the target since it already implicitly implements Runnable interface!
Ont tip: Always treat Runnable objects as some "work"/"job" and Thread objects as "workers". So, workers are given job to do!
Thread t/*the worker*/ = new Thread(new RunnableImplementor()/*this is the job*/);
t.start();//asking the worker to start doing the work
 
Annette Sovereign
Greenhorn
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Hi,

Thanks for responding.

I think my question was not clear.

I expect the code I pasted to fail as the Thread object is taking a subclass of Thread as an argument when being created which is not valid. I expect compilation to fail but according to the book I got the snippet of code this answer is wrong.

My question is - should compilation fail or not?

As always, I'd appreciate an explanation (I've already had a look at the API and it appears to support my reasoning).


Thanks.
 
Annette Sovereign
Greenhorn
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Hi,

Okay - so I decided to have a word with the compiler myself and he/she/it did not complain. So I guessed I must be wrong and the book correct (why isn't there a humble pie smiley??).

Anyway, I think I've figured it out now and know where I went wrong (when answering the question, I reeled off the list of constructors in my head).

Thanks to those that responded.

Happy Studying
 
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