@Override
    public Collection<V> values() {
        if (size == 0) {
            return Collections.emptySet();
        }
        List<V> list = new ArrayList<>(size);
        for (V element : values) {
            if (element != null) {
                list.add(element);
            }
        }
        return list;
    }
@author James Chen
@see java.util.EnumMap
turms-server-common/src/main/java/im/turms/server/common/infra/collection/FastEnumMap.java