Java:并行编程及同步使用方法

public class UploadFileToTask implements Callable<UploadFileToTaskResult> {
    private final Task_UploadFileToTaskItem taskItem;
    private final Log log = LogHelper.getInstance(ImportMain.class);
    private final CountDownLatch threadsSignal;
    private final HDFSUtil hdfsUtil = new HDFSUtil();
    private final static String HADOOP_HDFS_PATH = HdfsConfiguration.getHdfsUrl();

    public UploadFileToTask(CountDownLatch threadsSignal ,Task_UploadFileToTaskItem taskItem){
        this.taskItem=taskItem;
        this.threadsSignal=threadsSignal;
    }

    @Override
    public UploadFileToTaskResult call() throws Exception {
        String area = taskItem.getArea();
        String fileGenerateDate = taskItem.getFileGenerateDate();
        String manufacturer = taskItem.getManufacturer();
        String eNodeBId = taskItem.geteNodeBId();
        String filePath = taskItem.getFilePath();
        FileType fileType = taskItem.getFileType();

        TaskStatus taskStatus= TaskStatus.Success;

        // 不确定该FileSystem是否是线程安全的，故在每一个thread初始化一次。
        Configuration conf = new Configuration();
        Path dstPath = new Path(HADOOP_HDFS_PATH);
        FileSystem hdfs = dstPath.getFileSystem(conf);

        // 核心代码。。。
        // 上传MR文件
        // 上传Signal文件

        // 如果文件路径不为空，就开始上传文件到hdfs
        if(uploadFilePath.length()>0){
            if (!hdfsUtil.uploadFileToHdfs(hdfs, filePath, uploadFilePath)) {
                taskStatus= TaskStatus.Fail;
            }
        }

        TaskGroupInfo taskGroupInfo = new TaskGroupInfo();
        taskGroupInfo.setArea(area);
        taskGroupInfo.setManufacturer(manufacturer);
        taskGroupInfo.setFileGenerateDate(fileGenerateDate);
        taskGroupInfo.setFileType(fileType);

        String key = String.format("%s,%s,%s,%s", taskGroupInfo.getArea(), taskGroupInfo.getManufacturer(), taskGroupInfo.getFileGenerateDate(), String.valueOf(taskGroupInfo.getFileType().getValue()));

        UploadFileToTaskResult result=new UploadFileToTaskResult();

        // 填充返回值
        result.setStatus(taskStatus);
        result.setTaskGroupInfo(taskGroupInfo);
        result.setTaskGroupkey(key);
        result.setTaskOID(taskItem.getOid());

        System.out.println("task id:" + taskItem.getOid() + " >>>>线程名称:" + Thread.currentThread().getName() + "结束. 还有" + threadsSignal.getCount() + " 个线程");

        // 必须等核心处理逻辑处理完成后才可以减1
        this.threadsSignal.countDown();

        return result;
    }
}

            // 获取当前节点带执行任务
            ArrayList<Task_UploadFileToTaskItem> taskItems = uploadFileToTaskItemDao.getTopNTodoTaskItems(this.computeNode.getId(),Configuration.getTaskCount());
            // 批量修改任务状态为正在处理状态（doing）。
            log.info("Start:>>>>>>batch modify task status(doing)>>>>>>");
            log.info("Over:>>>>>>batch modify task status(doing)>>>>>>");

            // 批量处理上传任务（上传文件到）
            log.info("Start:>>>>>>each process task(upload to)>>>>>>");

            CountDownLatch threadsSignal = new CountDownLatch(taskItems.size());
            ExecutorService executor = Executors.newFixedThreadPool(taskItems.size());
            List<Future<UploadFileToTaskResult>> resultLazyItems=new ArrayList<Future<UploadFileToTaskResult>>();
            for (Task_UploadFileToTaskItem taskItem : taskItems) {
                // 使用future存储子线程执行后返回结果，必须在所有子线程都完成后才可以使用get();
                // 如果在这里使用get(),会造成等待同步。
                Future<UploadFileToTaskResult> future = executor.submit(new UploadFileToTask(threadsSignal,taskItem));
                resultLazyItems.add(future);
            }
            // 等待所有并行子线程任务完成。
            threadsSignal.await();
            executor.shutdown();//并不是终止线程的运行，而是禁止在这个Executor中添加新的任务 
            log.info("Over:>>>>>>each process task(upload to)>>>>>>");

            // 批量修改任务处理状态
            Map<String, TaskGroupInfo> taskGroupItems=new HashMap<String, TaskGroupInfo>();
            Map<Integer, TaskStatus> successTaskItems = new HashMap<Integer, TaskStatus>();
            Map<Integer, TaskStatus> failTaskItems = new HashMap<Integer, TaskStatus>();

            for(Future<UploadFileToTaskResult> future :resultLazyItems){
                UploadFileToTaskResult result= future.get();
                if(!taskGroupItems.containsKey(result.getTaskGroupkey())){
                    taskGroupItems.put(result.getTaskGroupkey(),result.getTaskGroupInfo());
                }
                if(result.getStatus()== TaskStatus.Success){
                    successTaskItems.put(result.getTaskOID(),result.getStatus());
                }else{
                    failTaskItems.put(result.getTaskOID(),result.getStatus());
                }
            }