Threads should not be Cloneable

[Chris Hegarty]

The issue of whether Threads should be Cloneable came up during the 
discussion of another problem. I talked to David about this and we 
believe there is no value being able to clone a thread, in fact it can 
cause some strange problems. David sent a mail [1] to the 
concurrency-interest mailing list requesting feedback on this. No 
objections to date.

To that end, I filed CR 6968584: "Thread should not be Cloneable" and am 
proposing to add the following to Thread:

    /**
     * Throws CloneNotSupportedException as a Thread can not be 
meaningfully
     * cloned. Construct a new Thread instead.
     *
     * @throws  CloneNotSupportedException
     *          always
     */
    protected final Object clone() throws CloneNotSupportedException {
        throw new CloneNotSupportedException();
    }

Thanks,
-Chris.

[1] 
http://cs.oswego.edu/pipermail/concurrency-interest/2010-August/007326.html