If you are using Initialize2, then the Clear method does not work.
java.lang.UnsupportedOperationException
B4X:
Dim lst As List
lst.Initialize2(Array As String("One", "Two", "Three"))
'lst.Initialize
'lst.Add("One")
'lst.Add("Two")
'lst.Add("Three")
lst.Clear
java.lang.UnsupportedOperationException