Question

Iam using below code for uploading images on the remote server.When I use below it is uploading all images cocurrently on remote server.

List<Future<String>> futureList = new ArrayList<Future<String>>();
ExecutorService execService = Executors.newFixedThreadPool(Images.size());
for (IImage image : Images) { 
  try {
    //execService.execute(lServerRequest.new uploadImages(image.getDataPath(),image.getDisplayName()));
    singleFuture = execService.submit(lServerRequest.new uploadImages(image.getDataPath(),image.getDisplayName()));
    //Log.d("","singleFuture -------"+singleFuture.get());
    futureList.add(singleFuture);
    Log.d("","futureList Size:"+futureList.size());
  } catch(Exception e){
    execService.shutdown();
  }

Whenever i used below code

   singleFuture = execService.submit(lServerRequest.new uploadImages(image.getDataPath(),image.getDisplayName()));
//Log.d("","singleFuture -------"+singleFuture.get());
    futureList.add(singleFuture);

adds all the future objects to futurelist immediately returning from runnable(not waiting in runnable until completion of uploading of all images(background uploading processing is going)

But whenever i uncommented below line in above code ,after successful uploading of every image it returns from runnable.

singleFuture = execService.submit(lServerRequest.new uploadImages(image.getDataPath(),image.getDisplayName()));
Log.d("","singleFuture -------"+singleFuture.get());
futureList.add(singleFuture);

is there anything wrong in my code and is it ok to take remote server connection more at a time or any load is on server?How to upload the images by using cocurrent programming java?Please give us guidance?

Do the submit() and execute() functions have the same effect?

Answer 1

When you call singleFuture.get() you are waiting for the operation to complete. So the loop won’t continue to execute next statement until this one returns a result.

You need to submit your tasks in the first loop and after that, another loop should iterate over the results future.get() on your list to make it async

From @andersoj’s answer;

The Pool size should be something related to your CPU cores. Not the number of images you have in hand. Say if you have 2 cored CPU, a coefficient of 5 (just my guess of coefficient) for image uploading io time.

POOL_SIZE = NUM_OF_CPU_CORE*coeffiecient;