According to the documentation of the Java Condition interface:
When waiting upon a Condition, a "spurious wakeup" is permitted to occur, in general, as a concession to the underlying platform
semantics. This has little practical impact on most application programs as a Condition should always be waited upon in a loop, testing the state
predicate that is being waited for. An implementation is free to remove the possibility of spurious wakeups but it is recommended that applications
programmers always assume that they can occur and so always wait in a loop.
The same advice is also found for the Object.wait(...) method:
waits should always occur in loops, like this one:
synchronized (obj) {
while (<condition does not hold>){
obj.wait(timeout);
}
... // Perform action appropriate to condition
}
Noncompliant Code Example
synchronized (obj) {
if (!suitableCondition()){
obj.wait(timeout); //the thread can wake up even if the condition is still false
}
... // Perform action appropriate to condition
}
Compliant Solution
synchronized (obj) {
while (!suitableCondition()){
obj.wait(timeout);
}
... // Perform action appropriate to condition
}
See
- CERT THI03-J. - Always invoke wait() and await() methods inside a loop
