初始化线程池大小和获取线程池实例

  private void initThreadPool()
    {
        int i = Runtime.getRuntime().availableProcessors() * 2;//默认处理器的2倍，最小为5
        if(threadPoolSize < i)
            threadPoolSize = i;
        if(threadPoolSize < 5)
            threadPoolSize = 5;
        int j = threadPoolSize;
        threadPool = new ThreadPoolExecutor(threadPoolSize, j, 30L, TimeUnit.SECONDS, new ArrayBlockingQueue(10000), new java.util.concurrent.ThreadPoolExecutor.DiscardOldestPolicy());
    }
//实例化
public static TaskPool getInstance()
    {
        if(instance == null)
            synchronized(this)
            {
                if(instance == null)
                {
                    TaskPool taskpool = new TaskPool();
                    taskpool.initThreadPool();
                    instance = taskpool;
                }
            }
        return instance;
    }