#fixed code
                                public String getLastBlockHash() throws Exception {
        byte[] lastBlockHashBytes = rocksDB.get(SerializeUtils.serialize(BLOCKS_BUCKET_PREFIX + "l"));
        if (lastBlockHashBytes != null) {
            return (String) SerializeUtils.deserialize(lastBlockHashBytes);
        }
        return "";
    }
#vulnerable code 
                                public String getLastBlockHash() throws Exception {
        byte[] lastBlockHashBytes = rocksDB.get((BLOCKS_BUCKET_PREFIX + "l").getBytes());
        if (lastBlockHashBytes != null) {
            return new String(lastBlockHashBytes);
        }
        return "";
    } 
                            #location 2 
                            #vulnerability type THREAD_SAFETY_VIOLATION