Maybe I am just not understanding how singletons work... there is only one instance of my singleton class, it has onemethod called write, which writes a file out to disk. Senario: Client A calls write, Client B calls write What happens? Does B wait on A? does B overwrite A? How are multiple calls to the same method in a singleton class handled?
Basically, there is no more problem with a Singleton class than with any other type of classes regarding your example. In your case, it may judicious to choose a Singleton to handle file access and ensure that only one client access at the file at a given time. In the nominal case, Client A calls write on the Singleton, then Client B calls write on the Singleton. This action for B is performed when the Singleton is over with writing with class A. Now if the calls to write are done in two different threads, then you have to be careful. You must bracket the critical section in a synchronized block. The writing for class A can then not be interrupted by class B. W.
Rob Bass
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Joined: Aug 28, 2001
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The write method is part of the Singleton class, so it should be ok, as the Singelton just has one instance.
Hi Rob! Yes, the Singleton class has only one instance, but it is possible to start many threads on one single instance, right? If two threads, both started on this lone instance, happen to call the write method simultaneously, there will be trouble. The only way to bypass this problem is to synchronize either the method or part of it (the critical parts; where you write to the disk). In other words, just like Wilfried said. Hope this helps! //Kaspar
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