private Shard getShard(final String className) {
        int idx = className.hashCode() % SHARD_NUM;

        if (idx < 0) {
            idx += SHARD_NUM;
        }

        return shards[idx];
    }
@author Jongho Moon
@author jaehong.kim
agent-module/plugins/spring/src/main/java/com/navercorp/pinpoint/plugin/spring/beans/interceptor/Cache.java