I have a List in my java file java util List and i have a fu kotlinlang #announcements

I have a List in my java file. java.util.List, and i have a function in my kotlin class which add theese items to a mutableList. I get UnsupportedOperationException and i can"t solve it with stackoverFlow posts. What can I do?

diesieben07

12/09/2019, 8:24 AM

How is

myMutableList

created? And can you show the stacktrace?

fradiati

12/09/2019, 8:26 AM

this is my adapter

abstract class BaseRecyclerAdapter<T>(
       private var masterList: MutableList<T> = mutableListOf()
) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

fun updateList(list: List<T>) {
    masterList.clear()
    masterList.addAll(list as MutableList<T>)
    notifyDataSetChanged()
}

diesieben07

12/09/2019, 8:27 AM

Why are you casting to

MutableList<T>

addAll

accepts a plain

List<T>

, no need for a mutable list.

fradiati

12/09/2019, 8:27 AM

2019-12-09 09:19:55.307 12705-12705 E/AndroidRuntime: FATAL EXCEPTION: main Process: com.velemjaro.app.debug, PID: 12705 java.lang.UnsupportedOperationException at java.util.AbstractList.add(AbstractList.java:148) at java.util.AbstractList.add(AbstractList.java:108) at java.util.AbstractCollection.addAll(AbstractCollection.java:344) at BaseRecyclerAdapter.updateList(BaseRecyclerViewAdapter.kt:12)

yes i know, but i try everything yes

diesieben07

12/09/2019, 8:28 AM

And that error should be impossible to get with that code, because

mutableListOf

returns an

ArrayList

, which overrides

add

fradiati

12/09/2019, 8:28 AM

yet

so it was my original function

fun updateList(list: List<T>) {
    masterList.clear()
    masterList.addAll(list)
    notifyDataSetChanged()
}

but i get this error every time

adapterBlog.updateList((List<BlogPost>) results);

diesieben07

12/09/2019, 8:29 AM

If you put a breakpoint at the start of that method, is

masterList

still an

ArrayList

fradiati

12/09/2019, 8:32 AM

masterList = {Collections$EmptryList@19456} size = 0

diesieben07

12/09/2019, 8:33 AM

Are you assigning

masterList

anywhere else? Like

masterList = ...

anywhere?

fradiati

12/09/2019, 8:34 AM

just in the constructor

diesieben07

12/09/2019, 8:34 AM

But then it can't be

Collections.EmptyList

...

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