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- A write to a variable does not depend on its current value.
- A write to a variable does not depend on the result of any non-atomic compound operations involving reads and writes of other variables. (For more information, see CON02 VNA02-J. Ensure that compound operations on shared variables are atomic.)
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The first condition can be relaxed when you can be sure that only one thread will ever update the value of the variable \[[Goetz 06|AA. Java References#Goetz 06]\]. However, code that relies on an invariant such as single-thread confinement to be true at all times is error-prone and difficult to maintain. This behavior is permissible under this guideline but not recommended. |
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Synchronization is a more secure alternative in situations where the volatile keyword or a java.util.concurrent.atomic.Atomic* field is inappropriate, such as if a variable's new value depends on its current value. For more information, see CON02 VNA02-J. Ensure that compound operations on shared variables are atomic.
Compliance with CON07-J. Use private final lock objects to synchronize classes that may interact with untrusted code can reduce the likelihood of misuse by ensuring that untrusted callers cannot access the lock object.
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