Android Tutorial [B4X][OOP] Generic Sorter

Erel

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The Sorter class uses quick sort algorithm to sort a list of objects.

There are exactly three assumptions about the list items:
1. All the items in the list are of the same type (or each item can be compared with all other items).
2. The item's class has a sub named CompareTo and it follows the following contract:
B4X:
'Returns -1 if this < other
'Returns 0 if equal
'Returns 1 if this > other
Public Sub CompareTo (Other As MyType) As Int
3. You are free to use whichever comparison logic you like. However it must be consistent:
A > B means that B < A
A = B means that B = A
A < B means that B > A

The Sorter class code is not familiar with any implementation or type. It just calls the CompareTo method:
B4X:
If CallSub2(Data.Get(i), "CompareTo", pivotValue) <= 0 Then
Usage example:
B4X:
Sub Activity_Create(FirstTime As Boolean)
   If FirstTime Then
     sort.Initialize
   End If
   Dim transactions As List
   transactions.Initialize
   For i = 1 To 30
     Dim t As Transaction
     'Price, Amount
     t.Initialize(Rnd(1, 100), Rnd(1, 10))
     transactions.Add(t)
   Next
   'sorts the transactions based on Price * Amount
   sort.SortList(transactions)
   For Each t As Transaction In transactions
     Log(t)
   Next
   Dim gibb As List
   gibb.Initialize
   For i = 1 To 30
     Dim g As Gibberish
     g.Initialize
     gibb.Add(g)
   Next
   'Sorts the Gibberish items based on the text length
   sort.SortList(gibb)
   For Each g As Gibberish In gibb
     Log(g)
   Next
End Sub
The classes are compatible with B4A, B4i and B4J.
 

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