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Compound operations on shared variables are also non-atomic. For more information, see guideline rule VNA02-J. Ensure that compound operations on shared variables are atomic.
Guideline Rule VNA04-J. Ensure that calls to chained methods are atomic describes a specialized case of this guidelinerule.
Noncompliant Code Example (AtomicReference)
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This technique is also called client-side locking \[[Goetz 2006|AA. Bibliography#Goetz 06]\] because the class holds a lock on an object that might be accessible to other classes. Client-side locking is not always an appropriate strategy; see guidelinerule [LCK11-J. Avoid client-side locking when using classes that do not commit to their locking strategy] for more information. |
This code does not violate guideline rule LCK04-J. Do not synchronize on a collection view if the backing collection is accessible because, while it does synchronize on a collection view (the synchronizedList), the backing collection is inaccessible and therefore cannot be modified by any code.
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This compliant solution avoids using Collections.synchronizedMap() because locking on the unsynchronized map provides sufficient thread-safety for this application. Guideline Rule LCK04-J. Do not synchronize on a collection view if the backing collection is accessible provides more information about synchronizing on synchronizedMap objects.
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Any vulnerabilities resulting from the violation of this guideline rule are listed on the CERT website.
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