B4J Question How to use a class in a class definition

Sub Class_Globals
    Private x As Float
    Private y As Float
End Sub

Public Sub Initialize As Tuple
    Return Me
End Sub

Public Sub Add(pXY As Tuple) As Tuple
    Dim result As Tuple
    result.Initialize
    result.x = x + pXY.x
    result.y = y + pXY.y
    Return result
End Sub


Public Sub Subtract(pXY As Tuple) As Tuple
    Dim result As Tuple
    result.Initialize
    result.x = x - pXY.x
    result.y = y - pXY.y
    Return result
End Sub

'This is a very useful tuplet creator - avoids many 'Initialize' lines
Public Sub XY(pX As Float, pY As Float) As Tuple
    Dim result As Tuple
    result.Initialize
    result.x = pX
    result.y = pY
    Return result
End Sub

Sub Class_Globals
    Private Root As B4XView    'ignore
    Private xui As XUI   
    Private pz As Tuple
End Sub

Public Sub Initialize
    pz.Initialize
End Sub

Private Sub B4XPage_Created (Root1 As B4XView)
    Root = Root1
    someSub
End Sub

Sub someSub
    Dim p0 As Tuple = pz.XY(100, 5)
    Dim p1 As Tuple = pz.XY(-100, -5)
    Dim sum As Tuple = p0.Add(p1)
    Dim dif As Tuple = p0.Subtract(p1)
    Dim more As Tuple = p0.Add(pz.XY(25, 35)).Subtract(pz.XY(5, 5))
    Log(p0)    'x=100.0, y=5.0
    Log(p1)    'x=-100.0, y=-5.0
    Log(sum)    'x=0.0, y=0.0
    Log(dif)    'x=200.0, y=10.0
    Log(more)    'x=120.0, y=35.0
End Sub

'This is a simple sub to log the contents of global variables of any class
Public Sub show As Tuple
    Dim str As String = Me
    Log(str.SubString2(1, str.IndexOf(", main")))
    Return Me
End Sub

Sub someSub
    Dim p0 As Tuple = pz.XY(100, 5).show
    Dim p1 As Tuple = pz.XY(-100, -5).show
    Dim sum As Tuple = p0.Add(p1)
    Dim dif As Tuple = p0.Subtract(p1)
    Dim more As Tuple = p0.Add(pz.XY(25, 35)).Subtract(pz.XY(5, 5))
    sum.show
    dif.show
    more.show
   
'    x=100.0, y=5.0
'    x=-100.0, y=-5.0
'    x=0.0, y=0.0
'    x=200.0, y=10.0
'    x=120.0, y=35.0
End Sub