Question

Could you tell me if I should release lock before await on condition?

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

Or

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

Answer 1

No, you do not need to explicitly release the lock before calling await, await will release it automatically. From javadoc:

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

And:

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