#vulnerable code 
                                public boolean lock(long seckillId) {
        try {
            Map<Long, InterProcessMutex> map;
            String rootLockPath = "/goodskill";
            if (threadLock.get() == null) {
                map = new ConcurrentHashMap();
                map.put(seckillId, new InterProcessMutex(client, rootLockPath + "/" + seckillId));
                threadLock.set(map);
            } else {
                if (threadLock.get().get(seckillId) == null) {
                    map = threadLock.get();
                    map.put(seckillId, new InterProcessMutex(client, rootLockPath + "/" + seckillId));
                }
            }
            boolean acquire = threadLock.get().get(seckillId).acquire(5000L, TimeUnit.MILLISECONDS);
            if (log.isDebugEnabled()) {
                log.debug("成功获取到zk锁,秒杀id{}", seckillId);
            }
            return acquire;
        } catch (Exception e) {
            log.warn("获取zk锁异常:{}", e.getMessage());
            return false;
        }
    } 
                            #location 15 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public boolean lock(long seckillId) {
        try {
            Map<Long, InterProcessMutex> map;
            String rootLockPath = "/goodskill";
            Map<Long, InterProcessMutex> processMutexMap = threadLock.get();
            if (processMutexMap.get(seckillId) == null) {
                processMutexMap.put(seckillId, new InterProcessMutex(client, rootLockPath + "/" + seckillId));
            }
            boolean acquire = processMutexMap.get(seckillId).acquire(5000L, TimeUnit.MILLISECONDS);
            if (log.isDebugEnabled()) {
                log.debug("成功获取到zk锁,秒杀id{}", seckillId);
            }
            return acquire;
        } catch (Exception e) {
            log.warn("获取zk锁异常:{}", e.getMessage());
            return false;
        }
    }