public void retainAllUsers(Collection<String> users) {
Lock lock = xLock.writeLock();
lock.lock();
try {
X.removeAll(new NotContainsPredicate<>(users));
} finally {
lock.unlock();
}
}
public void retainAllItems(Collection<String> items) {
Lock lock = yLock.writeLock();
lock.lock();
try {
Y.removeAll(new NotContainsPredicate<>(items));
} finally {
lock.unlock();
}
}