#vulnerable code 
                                public void putLastBlockHash(String tipBlockHash) throws Exception {
        rocksDB.put((BLOCKS_BUCKET_PREFIX + "l").getBytes(), tipBlockHash.getBytes());
    } 
                            #location 2 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                public void putLastBlockHash(String tipBlockHash) throws Exception {
        rocksDB.put(SerializeUtils.serialize(BLOCKS_BUCKET_PREFIX + "l"), SerializeUtils.serialize(tipBlockHash));
    }