java - 条件 - 应该在等待之前解锁吗？

Question

你能告诉我是否应该在条件等待之前释放锁吗？

try {
    lock.lock();
    while (isNotEmpty()) {
        condition.await();
    }
} finally {
    lock.unlock();
}

或者

try {
    lock.lock();
    while (isNotEmpty()) {
        lock.unlock();
        condition.await();
    }
} finally {
    lock.unlock();
}

Answer 1

不，你不需要在调用await之前显式释放锁，await会自动释放它。来自 javadoc :

The lock associated with this Condition is atomically released and the current thread becomes disabled for thread scheduling purposes[...]

和:

The current thread is assumed to hold the lock associated with this Condition when this method is called.