Awesome, Ive also checked this, and it seems reliable.
B4X:
Dim l As List
l.Initialize
For c = 0 To 1000000
l.Add(c)
Next
File.WriteList(File.DirApp,"out.txt",l)
Dim l2 As List = File.ReadList(File.DirApp,"out.txt")
Log(l2.Get(0))
Log(l2.Get(l2.Size-1))