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Read-write locks allow shared state to be accessed by multiple readers or a single writer but never both. According to Goetz \[[Goetz 06|AA. Java References#Goetz 06]\]: |
In practice, read-write locks can improve performance for frequently accessed read-mostly data structures on multiprocessor systems; under other conditions they perform slightly worse than exclusive locks due to their greater complexity.
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The flag variable is updated using the compareAndSet() method of the AtomicBoolean class. All updates are visible to other threads.
Noncompliant Code Example (Addition of
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Primitives)
In this noncompliant code example, multiple threads can invoke the setValues() method to set the a and b fields. Because this class does not test for integer overflow, a user of the Adder class must ensure that the arguments to the setValues() method can be added without overflow. (For more information, see INT00-J. Perform explicit range checking to ensure integer operations do not overflow.)
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Note that declaring the variables as volatile does not resolve the issue because these compound operations involve reads and writes of multiple variables.
Noncompliant Code Example (Addition of
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Atomic Integers)
In this noncompliant code example, a and b are replaced with atomic integers.
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