如何在具有线程安全的多个swing工作者线程中使用Instance变量？

Question

I am using swing worker thread to communicate rest services. My scenerio is i am calling one thread to get the data from rest services and add into my list variable . and another one thread to push the list of data to save it. How to handle this scenerio with thread safe

My sample code is below

  private LinkedList<LinkInfo> ***linkInfoList*** = new LinkedList<FlowLinkEntry>();

 SwingWorker<LinkInfo, Void> loadLinkInfoThread = new SwingWorker<LinkInfo, Void>() {

        @Override
        protected LinkInfo doInBackground() throws Exception {

            InputStream is = new URL("Http://URL").openStream();
            try {
                BufferedReader reader = new BufferedReader(
                        new InputStreamReader(is,
                                Charset.forName("UTF-8")));
                LinkInfo linkInfo = (LinkInfo)JsonConverter
                        .fromJson(reader, LinkInfo.class);
                ***linkInfoList*** .add(linkInfo);

            } finally {
                is .close();
            }
            return linkInfo;
        }
}


 SwingWorker<Void, Void> saveLinkInfoThread = new SwingWorker<Void, Void>() {

        @Override
        protected Void doInBackground() throws Exception {
            //post data to particular url   
            //linkInfoList data is posting in this thread 

            URL url = new URL(http://url);
            URLConnection conn = url.openConnection();
            conn.setDoOutput(true);
            OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
            wr.write(***linkInfoList*** );
            wr.flush();
            // Get the response
            BufferedReader rd = new BufferedReader(new InputStreamReader(
            conn.getInputStream()));

        }

}

My questions are

1. How to store the data in linkInfoList as request order wise? (ie) if i call load thread several time,the data should inserted in list request wise.

2. How to put wait state the save Thread if load Thread is already in progress. I mean that if load thread is in running condition, after completing load thread then only save thread should have to run

Answer 1

I would synchronize list at initialization as Oracle says .

List ***linkInfoList*** = Collections.synchronizedList(new LinkedList(...));

Then you would have to test the list if there are any items to save, otherwise wait.

SwingWorker<Void, Void> saveLinkInfoThread = new SwingWorker<Void, Void>() {

    @Override
 protected Void doInBackground() throws Exception {

      List info = new ArrayList();
      while (***linkInfoList***.isEmpty()){
           Thread.currentThread().sleep(1000);
      }
      while (!***linkInfoList***.isEmpty()){
           info.add(***linkInfoList***.remove(0));
      }



      //post data to particular url   
      //linkInfoList data is posting in this thread 

      URL url = new URL(http://url);
      URLConnection conn = url.openConnection();
      conn.setDoOutput(true);
      OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());


      wr.write(info);
      wr.flush();
      // Get the response
      BufferedReader rd = new BufferedReader(new InputStreamReader(
      conn.getInputStream()));

    }