I have developed an android app using the latest alpha version of Jetpack Compose.
All relevant files are available in the BobbleBigText folder
More details about this app are available here
Please note that since Jetpack Compose is in alpha, the app won't perform as well as other apps. Building a standard app with Views and RecyclerView would have been easy but I wanted to try this app using Compose.
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:859)
at java.util.ArrayList$Itr.next(ArrayList.java:831)
at main.java.Bobble.main(Test.java:25)
There could be multiple things going wrong here depending on how the ArrayList is being used -
- The ArrayList might have been modified concurrently by 2 different threads. This only happens in multi-threaded environments. However, the next error I mention is more likely:
- Modifying the ArrayList while iterating through it.
A common mistake many people make is modify an ArrayList like this:-
val list = ArrayList<Int>()
list.addAll(....)
for(item in list) {
if(item >= 2 && item <= 6)
list.remove(item)Here, the list is being modified while we are iterating over it. This results in the above-mentioned error being thrown. The above code can also be used to reproduce this error.
A simple fix for the above problem is to use an iterator instead of manually iterating over the list. So the above code becomes:-
val list = ArrayList<Int>()
list.addAll(....)
val iterator = list.iterator()
while(iterator.hasNext()) {
val item = iterator.next()
if(item >= 2 && item <= 6)
iterator.remove()
}The above code does exactly the same thing - Remove all numbers between 2 and 6 (both inclusive) from the ArrayList.
However, the main difference being iterator#remove() calls are safe.
Another possible alternative is to add all the elements you intend to remove in a separate list and use ArrayList#removeAll().
In case the above was not the use-case and the arrayList was being used by multiple threads, it can also result in the mentioned error.
In such a case, there are 2 possible solutions:-
- Use Vector instead of ArrayList. ArrayList is not synchronized while Vector is.
- Lock any list modifications in a synchronized block. This prevents multiple threads from accessing it at the same time.
I am an android developer and a kotlin enthusiast. I am currently trying out new tools and improving my knowledge of tools available on android. You can find some of my common profiles below:-