在我的情况下是锁+HasMap还是ConcurrentHashMap？

Question

    private static ReentrantLock lock_Vqueue = new ReentrantLock();
    private static HashMap<String,Queue<DocumentObjectHolder>> cacheData = new HashMap<String,Queue<DocumentObjectHolder>>();
        /**
         * insert element in the tail 
         * sort the elements by priority 
         * @param obj a DocumentObjectHolder Object
         */
        public static void add(String key, DocumentObjectHolder obj){
            ReentrantLock lock = lock_Vqueue; //performance side effect
            try{
                Queue<DocumentObjectHolder>priorityProcessingVirtualQueue;
                lock.lock();
                    if (!cacheData.containsKey(key)){
                        priorityProcessingVirtualQueue = new PriorityQueue<DocumentObjectHolder>(1, new PriorityComparator());
                        cacheData.put(key, priorityProcessingVirtualQueue);
                    }
                    priorityProcessingVirtualQueue = cacheData.get(key);
                    priorityProcessingVirtualQueue.add(obj);
                    cacheData.put(key, priorityProcessingVirtualQueue);
            }finally {
                lock.unlock();
            }
        }

        /**
         * 
         * @return DocumentObjectHolder instance from head of list (FIFO)
         */
        public DocumentObjectHolder get(String key){
            ReentrantLock lock = lock_Vqueue; //performance side effect
            Queue<DocumentObjectHolder>priorityProcessingVirtualQueue;
            try {
                lock.lock(); 
                 if (cacheData.containsKey(key)){
                     priorityProcessingVirtualQueue = cacheData.get(key);
                     return priorityProcessingVirtualQueue.poll();
                 }
                 return null;
            }finally{
                lock.unlock();
            }
        }
}

这个代码是正确的还是性能更好？

Answer 1

因此您有两个单独的原子指令需要与之同步。

1. 将新队列放入映射
2. 将对象放入队列

以下是我的建议。

    public static void add(String key, DocumentObjectHolder obj){
        Queue<DocumentObjectHolder> priorityProcessingVirtualQueue= cacheData.get(key);
        if(priorityProcessingVirtualQueue== null){
             Queue<DocumentObjectHolder> temp = new PriorityQueue<DocumentObjectHolder>(1, new PriorityComparator());
             queue = cacheData.putIfAbsent(key, temp);
             if(priorityProcessingVirtualQueue== null){ 
                  priorityProcessingVirtualQueue= temp;
             } 
        }
        synchronized(priorityProcessingVirtualQueue){
            priorityProcessingVirtualQueue.add(obj);
        }
    }