Instances of classes that implement either or both of the
Condition interfaces of the
java.util.concurrent.locks package are known as high-level concurrency objects. Using the intrinsic locks of such objects is a questionable practice even in cases where the code may appear to function correctly. Code that uses the intrinsic lock of a
Lock object is likely to interact with code that uses the
Lock interface. These two components will believe they are protecting data with the same lock, while they are, in fact, using two distinct locks. As such, the
Lock will fail to protect any data.
Consequently, programs that interact with such objects must use only the high-level locking facilities provided by the interfaces; use of the intrinsic locks is prohibited. This problem generally arises when code is refactored from intrinsic locking to the
java.util.concurrent dynamic-locking utilities.
Noncompliant Code Example (
doSomething() method in this noncompliant code example synchronizes on the intrinsic lock of an instance of
ReentrantLock rather than on the reentrant mutual exclusion
Lock encapsulated by
Compliant Solution (
This compliant solution uses the
unlock() methods provided by the
In the absence of a requirement for the advanced functionality of the
java.util.concurrent package's dynamic-locking utilities, it is better to use other concurrency primitives such as synchronization and atomic classes.
Synchronizing on the intrinsic lock of high-level concurrency utilities can cause nondeterministic behavior resulting from inconsistent locking policies.