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This idiom can also be suitably used by classes designed for inheritance. If a superclass thread requests a lock on the class object's monitor, a subclass thread can interfere with its operation. Refer to the guideline CON01CON02-J. Always synchronize on the appropriate object for more details.
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For more details on using the private Object lock refer to CON01CON02-J. Always synchronize on the appropriate object. There is some performance impact associated with using block synchronization instead of method synchronization but the difference is usually negligible.
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