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This code does not violate CON40-J. Do not synchronize on a collection view if the backing collection is still accessible, because while it does synchronize on a collectoin view (the synchronizedList), the backing collection is not accessible, and hence cannot be modified by any code.
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This compliant solution does not use Collections.synchronizedMap() because locking on the (unsynchronized) map provides sufficient thread-safety for this application. The guideline CON40-J. Do not synchronize on a collection view if the backing collection is still accessible provides more information about synchronizing on synchronizedMap objects.
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