RFIDReader | Windows driver for manually reading input

From the HashSet docs:

The iterators returned by this class's iterator method are fail-fast: if the set is modified at any time after the iterator is created, in any way except through the iterator's own remove method, the Iterator throws a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Basically, when you're iterating over a collection, you shouldn't modify that same collection - you'll see this same warning under HashMap, LinkedList etc. It causes unpredictable behaviour, and there are different changes you could make that would affect the current state in different ways, so they just make it fail and say "so don't do that!"

As for why it happens with large batches and not a single scan:

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis.

So it's probably just more likely that a large set of changes will get noticed. It goes on to say "don't rely on this behaviour" so you should probably do things in a different way! Usually you would just create a separate Set (an empty one, or a copy of your original) and make changes to that, and then return it or swap the original out for it when you're done.

Just to be clear, the problem here is that you're creating an iterator on a collection (with the for loop) and then modifying that collection while the iterator is running on it. I noticed you have synchronized on your method, so if you're also accessing the same collection on different threads, you have to make sure you're doing that in a thread-safe way too - the HashSet link talks a bit about that stuff

Yes, you can intercept the back button and do anything you want there (even cancel the back navigation), but then you'll miss the cases where the user leaves by the Home button, or an incoming call, or through a notification...

What you should do instead is to override the onPause, onStop, and/or, onDestroy methods for your activity. They are all callbacks related to the activity life cycle, which you will soon need to learn about.

In short: onPause happens when you lose focus, onStop when you're no longer visible, and onDestroy when the activity is fully deleted (e.g. the user pressed "back", but usually not when they pressed "home").

In your case, onStop is probably the most suitable one.

You can not simply cast a Set to a List you have to convert it like:

(java 8)

I don't know why are you trying always to convert to decimal? and please try to explain more about the code you use to read the UID.

about your numbers and to convert 17 digits to 10 digits; I convert both of them to Hex:

36139312876727556(17digit) in Hex : 8064837A71AD04.

2054270212(10 digit) in Hex: 7A71AD04

as you notice you can just tirm first three bytes to get the 10 digits.

and I do belive the both of them are not the UID. but the 7bytes as sayed Andrew, and you already read it in the your photo : (04:B5:71:7A:83:64:80)

Change this

I have tried a different approach following the instructions at raspberrypi-spy.co.uk/2018/02/rc522-rfid-tag-read-raspberry-pi using the library github.com/mxgxw/MFRC522-python. The output UID using this library for the tag I have is:

From the Docs:

Diagnosing This Error

When you get this error it can be rather daunting to diagnose the cause of the issue. The best course of action is to investigate the stack trace from the error. You need to look for places where $apply or $digest have been called and find the context in which this occurred.

There should be two calls:

The first call is the good $apply/$digest and would normally be triggered by some event near the top of the call stack.

The second call is the bad $apply/$digest and this is the one to investigate.

Once you have identified this call you work your way up the stack to see what the problem is.

If the second call was made in your application code then you should look at why this code has been called from within an $apply/$digest. It may be a simple oversight or maybe it fits with the sync/async scenario described earlier.

If the second call was made inside an AngularJS directive then it is likely that it matches the second programmatic event trigger scenario described earlier. In this case you may need to look further up the tree to what triggered the event in the first place

For more information, see AngularJS Error Reference - inprog - Diagnosing This Error.

1) Create getters in Adapter for your fields, ex