Java – ThreadPoolExecutor: get the specific runnable being executed

I am using ThreadPoolExecutor to execute multiple long-running tasks in the background. The pool size of ThreadPoolExecutor is 4. Therefore, when more than 4 tasks are added, they are pushed to the queue. When one of the 4 tasks is completed, a task is executed from the queue for execution

I want to know if there is a way to access the runnable objects that are currently executing but not in the queue, that is, the first four tasks

Purpose: I want to get the current status of the task at any given point, in mthreadpoolexecutor With the help of getqueue (), I am accessing the tasks queued and ready to execute. Please advise me to access the tasks currently executing, so that I can attach and delete the listener / handler on it when necessary

My runnable class:

public class VideoFileUploadRunner implements Runnable {

    private final VideoFileSync mVideoFileSync;
    private final DataService dataService;

    private Handler handler;

    public VideoFileUploadRunner(VideoFileSync videoFileSync,DataService dataService) {
        this.mVideoFileSync = videoFileSync;
        this.dataService = dataService;

    }

    public int getPK()
    {
        return  mVideoFileSync.get_idPrimaryKey();
    }

    public void setHandler(Handler handler) {
        this.handler = handler;
    }

    @Override
    public void run() {
        try {

            if (mVideoFileSync.get_idPrimaryKey() < 0) {
                addEntryToDataBase();
            }
            updateStatus(VideoUploadStatus.IN_PROGRESS);
            FileUploader uploader = new FileUploader();
            updateStatus(uploader.uploadFile(mVideoFileSync.getVideoFile()));



        } catch (Exception e) {
            updateStatus(VideoUploadStatus.Failed);
            e.printStackTrace();
        }
    }

    private void addEntryToDataBase() {
        int pk = dataService.saveVideoRecordForSync(mVideoFileSync);
        mVideoFileSync.set_idPrimaryKey(pk);
    }

    private void updateStatus(VideoUploadStatus status) {
        if (handler != null) {
            Message msg = new Message();
            Bundle b = new Bundle();
            b.putString(AppConstants.Sync_Status,status.toString());
            msg.setData(b);
            handler.sendMessage(msg);
        }
        dataService.updateUploadStatus(mVideoFileSync.get_idPrimaryKey(),status.toString());


    }
}

In the task progress list view:

public void setData(VideoFileSync fileSync) {
        tvIso.setText(fileSync.getVideoFile().getISO_LOOP_EQUP());
        tvUnit.setText(fileSync.getVideoFile().getUnit());
        tvName.setText(fileSync.getVideoFile().getLocalPath());
        tvStatus.setText(fileSync.getCurentStatus().toString());
        addHandleForUpdate(fileSync);
    }

    private void addHandleForUpdate(VideoFileSync fileSync) {

        Handler.Callback callBack = new Handler.Callback() {
            @Override
            public boolean handleMessage(Message msg) {
                if(msg.getData()!=null)
                {
                    tvStatus.setText(msg.getData().getString(AppConstants.Sync_Status));

                }
                return false;
            }
        };
        mHadler = new Handler(Looper.getMainLooper(),callBack);

        VideoFileUploadRunner runner = VideoUploadManager.getInstance().getRunnerForSyncFile(fileSync);
        if(runner!=null)
        runner.setHandler(mHadler);
    }

In videouploadmanager, I have the following methods to return the runnable object. Here I need help so that I can return the currently executing task

public synchronized VideoFileUploadRunner getRunnerForSyncFile(VideoFileSync fileSync) {
        Iterator<Runnable> itr = mThreadPoolExecutor.getQueue().iterator();
        while (itr.hasNext()) {
            VideoFileUploadRunner runner = (VideoFileUploadRunner) itr.next();
            if (runner.getPK() == fileSync.get_idPrimaryKey()) {
                return runner;
            }
        }
        return null;

    }

Solution

The best way is to expose a synchronization variable that contains information about the currently executing task

public MyTask implements Runnable {
    private String id;
    private Map<String,MyTask> mapTasks;

    public MyTask(String id,Map<String,MyTask> mapTasks) {
        this.id = id;
        this.mapTasks = mapTasks;
    }

    public void run() {
         synchronized(mapTasks) {
             mapTasks.put(id,this);
         }

         ...

         synchronized(mapTasks) {
             mapTasks.remove(id);
         }
    }
}


// Create a map of tasks
Map<String,MyTask> mapTasks = new HashMap<String,MyTask>();

// How to create tasks
MyTask myTask1 = new MyTask("task1",mapTasks);
MyTask myTask2 = new MyTask("task2",mapTasks);

executorService.execute(myTask1);
executorService.execute(myTask2);

....

And print the list of currently executing tasks:

public void printCurrentExecutingTasks(Map<String,MyTask> tasks) {
    for (String id: tasks.keySet()) {
        System.out.println("Executing task with id: " + id);
    }
}