What are spurious wakeups in Java?

What are spurious wakeups in Java?

Spurious wakeups in Java refer to situations where a thread wakes up from a waiting state without being notified. This can happen with methods like Object.wait(), Thread.sleep(), or LockSupport.park(). It's important to handle this correctly to avoid unexpected behavior.

How can I handle spurious wakeups in my code?

To handle spurious wakeups, you should always use a loop to check the condition after waking up. For example:

synchronized (lock) {
    while (!condition) {
        lock.wait();
    }
}

This ensures that even if a spurious wakeup occurs, the thread will recheck the condition.

Are there any best practices to avoid issues with spurious wakeups?

Yes, some best practices include:

1. Always use a loop to check conditions after waiting.
2. Minimize the time spent holding locks.
3. Use higher-level concurrency utilities from the java.util.concurrent package when possible.

Can you give an example of a spurious wakeup scenario?

Sure! Imagine a thread is waiting for a resource to become available. If it wakes up without being notified (a spurious wakeup), it might proceed to access the resource, which could lead to errors if the resource is still unavailable.