Question

I am trying to process multiple file writing commands (to seperate files) without hanging the UI.

To put my question in context, imagine the following

1. My main application looks like a file manager. It currently sees 10 files each of about 5MB in size. (Don’t worry about how this list works etc.)

2. When I select one file item, I want it to immediately start copying/duplicating the file onto another location on the SD card. Typically this should take a few seconds

3. I want to be able to select a second, or a third etc. file immediately after the first. At the end of everything, all the files which I selected will be duplicated. So I could, for example click 5 files within 5 seconds, but all the copying actions takes a minute.

At this moment two options have come to my mind:

The first is to simply put the file writing commands of each file in a seperate thread. Pseudocode will look like this

Onclick
   new Thread()
      write file

If this works, there can be scenarios where I have 10 threads running simultaneously, writing to 10 seperate files. I would like to know if anyone has done this before, and what I should be looking out for

The second option, of course, is if there is already a certain data structure/known methods that can address this problem. Some sort of a pending queue system that gets larger as I add requests, but gets smaller as the system writes the data away.

Answer 1

I’m not absolutely sure how the SD-card works, but I can tell you that trying to write in parallel to a single hard disk is a bad idea because it will actually slow down the performance compared to a sequential write.

You may want to try using an ExecutorService and measuring the performance with different thread counts but I’m afraid you will end up having to implement a queue with a single thread taking the queued files and writing them one by one.