| Description |
The Reverse method reverses the sequence of the elements in the ArrayList. All elements are reversed unless a range is specified via the StartIndex and Count parameters.
The Comparer parameter allows you to supply the comparison object used by the Sort method when it compares ArrayList Elements. The Compare method of Comparer is used.
Each element must implement the System.Collections.IComparer interface to facilitate the sort process.
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| Microsoft MSDN Links |
System.Collections
System.Collections.ArrayList
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| Sorting the whole ArrayList into sequence |
program Project1;
{$APPTYPE CONSOLE}
uses
System.Collections;
var
List : System.Collections.ArrayList;
i : Integer;
begin
// Create our array list object
List := ArrayList.Create;
// Fill it
List.Add('2.--');
List.Add('3.---');
List.Add('0.');
List.Add('1.-');
// Display List contents : note the 0 indexing
for i := 0 to List.Count-1 do
Console.WriteLine(List.Item[i]);
// Sort the array into sequence
Console.WriteLine;
Console.WriteLine('Sorting the array into sequence :');
Console.WriteLine;
List.Sort;
// Display List contents again
for i := 0 to List.Count-1 do
Console.WriteLine(List.Item[i]);
Console.Readline;
end.
| | Show full unit code | 2.--
3.---
0.
1.-
Sorting the array into sequence :
0.
1.-
2.--
3.---
| | | Sorting using an IComparer class object | program Project1;
{$APPTYPE CONSOLE}
uses
System.Collections;
type
// Define our data class
MyData = Class
private
daAge : Integer;
published
property Age : Integer
read daAge;
constructor Create(Age : Integer);
end;
// Define our comparer class
MyComparer = Class(TObject, System.Collections.IComparer)
published
function Compare(Object1 : System.Object;
Object2 : System.Object) : Integer;
end;
// Data class constructor
constructor MyData.Create(Age: Integer);
begin
Inherited Create;
daAge := Age;
end;
// Compare method of our comparer class
function MyComparer.Compare(Object1 : System.Object;
Object2 : System.Object) : Integer;
var
Data1, Data2 : MyData;
begin
// Protect our comparison in case of non-integer objects
try
// We cast the Object parameters to our Data type
Data1 := MyData(Object1);
Data2 := MyData(Object2);
// And compare : Return <1, 0 or >1 as appropriate
Result := Data1.Age - Data2.Age;
except
Result := 0;
end;
end;
// Main code
// ----------------------------------------------------------
var
List : System.Collections.ArrayList;
Comparer : MyComparer;
i : Integer;
begin
// Create our array list object
List := ArrayList.Create;
// Fill it
List.Add(MyData.Create(254));
List.Add(MyData.Create(2));
List.Add(MyData.Create(74));
List.Add(MyData.Create(11));
List.Add(MyData.Create(243));
List.Add(MyData.Create(55));
// Display List contents : note the 0 indexing
for i := 0 to List.Count-1 do
Console.WriteLine(MyData(List.Item[i]).Age.ToString);
// Create our comparer object
Comparer := MyComparer.Create;
// Sort the array into sequence
Console.WriteLine;
Console.WriteLine('Sorting the array into sequence :');
Console.WriteLine;
List.Sort(Comparer);
// Display List contents again
for i := 0 to List.Count-1 do
Console.WriteLine(MyData(List.Item[i]).Age.ToString);
Console.Readline;
end.
| | Show full unit code | 254
2
74
11
243
55
Sorting the array into sequence :
2
11
55
74
243
254
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