#vulnerable code 
                                public void init() {
        //load five(CACHE_COUNT) round from db on the start time ;
        Block bestBlock = getBestBlock();
        BlockRoundData roundData = new BlockRoundData(bestBlock.getHeader().getExtend());
        boolean updateCacheStatus = true;
        for (long i = roundData.getRoundIndex(); i >= 1 && i >= roundData.getRoundIndex() - CACHE_COUNT; i--) {
            Block firstBlock = getBlockService().getRoundFirstBlock(i - 1);
            BlockRoundData preRoundData = new BlockRoundData(firstBlock.getHeader().getExtend());
            PocMeetingRound round = calcRound(firstBlock.getHeader().getHeight(), i, preRoundData.getRoundEndTime(), updateCacheStatus);
            ROUND_MAP.put(round.getIndex(), round);
            Log.debug("load the round data index:{}", round.getIndex());
            updateCacheStatus = false;
        }
    } 
                            #location 7 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public void init() {
        lock.lock();
        try {
            realInit();
        } finally {
            lock.unlock();
        }
    }