{
This example demonstrates the usage of the generic TQueue class.
}
procedure TForm3.Button1Click(Sender: TObject);
var
  Queue: TQueue<String>;
begin
  { Create a new Queue }
  Queue := TQueue<String>.Create();

  { Register a notification call-back }
  Queue.OnNotify := QueueChanged;

  { Enqueue some items up the Queue }
  Queue.Enqueue('John');
  Queue.Enqueue('Mary');
  Queue.Enqueue('Bob');
  Queue.Enqueue('Anna');
  Queue.Enqueue('Erica');

  { Show the last enqueued element without modifying the Queue }
  MessageDlg('First enqueued element is: "' + Queue.Peek() + '".', mtInformation, [mbOK], 0);

  { Extract the top element: "Erica" }
  Queue.Extract();

  { Reduce the capacity }
  Queue.TrimExcess();

  { The remaining count of elements }
  MessageDlg('The queue contains ' + IntToStr(Queue.Count) + ' elements.', mtInformation, [mbOK], 0);

  { Show the last enqueued element by modifying the Queue }
  MessageDlg('First enqueued element is: "' + Queue.Dequeue() + '".', mtInformation, [mbOK], 0);

  { Clear the Queue }
  Queue.Clear();

  { Destroy the Queue completely }
  Queue.Free;
end;

procedure TForm3.QueueChanged(Sender: TObject; const Item: String; Action: TCollectionNotification);
begin
  { This method is called by the List everytime a change occurs }
  if Action = cnAdded then
     MessageDlg('Element added: ' + Item, mtInformation, [mbOK], 0)
  else if Action = cnRemoved then
     MessageDlg('Element removed: ' + Item, mtInformation, [mbOK], 0)
  else if Action = cnExtracted then
     MessageDlg('Element extracted: ' + Item, mtInformation, [mbOK], 0)
end;