Bug? B4J List.RemoveAt fails on List where Initialize2 used

[Bruce Axtens]

I've been messing with B4J for about a week, so the following may be due to naivety.

With this code

'Non-UI application (console / server application)
#Region  Project Attributes
    #CommandLineArgs:
    #MergeLibraries: True
#End Region

Sub Process_Globals
    Dim L1 As List
    Dim L2 As List
End Sub

Sub AppStart (Args() As String)
    L1.Initialize
    L1.Add(1)
    L1.Add(2)
    L1.Add(3)
    L1.Add(4)
    Log(L1)
    Log(L1.Size)
    L1.RemoveAt(0)
    Log(L1.Size)
    L1.clear
    Log(L1.Size)

    Log("--")
    L2.Initialize2(Array As Int(1,2,3,4))
    Log(L2)
    Log(L2.Size)
    L2.RemoveAt(0)
    Log(L2.Size)
    L2.clear
    Log(L2.Size)
End Sub

I get the following. What am I missing?

Program started.
(ArrayList) [1, 2, 3, 4]
4
3
0
--
(ArrayList) [1, 2, 3, 4]
4
Error occurred on line: 31 (main).
java.lang.UnsupportedOperationException
    at java.util.AbstractList.remove(AbstractList.java:161)
    at anywheresoftware.b4a.objects.collections.List.RemoveAt(List.java:92)
    at b4j.example.main._appstart(main.java:103)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:563)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:221)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:156)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:93)
    at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:82)
    at anywheresoftware.b4a.BA.raiseEvent(BA.java:84)
    at b4j.example.main.main(main.java:28)
Program terminated (StartMessageLoop was not called).

 

[Erel]

See List.Initialize2 documentation: http://www.b4x.com/b4j/help/collections.html#list_initialize2

 

[Bruce Axtens]

"and if you pass an array the list will be of a fixed size. Meaning that you cannot later add or remove items."

What I thought: naivety and not reading the friendly manual

 

[Erel]

The purpose if List.Initialize2 is to wrap an array. Not to create a new data collection.

Note that this method is not really required as the compiler will do it for you anyway:

Dim l1 As List = Array("a", "B") 'valid code

If you do want to create a dynamic list from an array then you should use List.AddAll.