undo, redo and delete function

[ivan12yu2000]

hi there,
I need to write these 3 functions, but i got stuck at redo and delete. Redo is showing error when there is nothing to redo and i don't know how to write delete function. Thank you
undo

package zadani21.commands;
import zadanie21.Command;
import zadanie21.Main;
import zadanie21.MyCanvas;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.ImageIcon;
import javax.swing.KeyStroke;
public class Undo extends AbstractAction {

	private MyCanvas myCanvas;

	public Undo(MyCanvas myCanvas) {
		this.myCanvas = myCanvas;
		this.putValue(NAME, "Undo");
		this.putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke("ctrl Z"));
		this.putValue(SMALL_ICON, new ImageIcon(Main.class.getResource("/icons/Undo24.gif")));
	}

	public void actionPerformed(ActionEvent e) {
		if (!myCanvas.commands.isEmpty()) {

			Command cmd = myCanvas.commands.pop();
			cmd.undo();
			myCanvas.undoneCommands.add(cmd);
			myCanvas.repaint();
		}
                else
                    System.out.println();
	}
}

redo

package zadani21.commands;

import zadanie21.Command;
import zadanie21.Main;
import zadanie21.MyCanvas;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.ImageIcon;
import javax.swing.KeyStroke;

public class Redo extends AbstractAction {

	private MyCanvas myCanvas;

	public Redo(MyCanvas myCanvas) {
		this.myCanvas = myCanvas;
		this.putValue(NAME, "Redo");
		this.putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke("ctrl Y"));
		this.putValue(SMALL_ICON, new ImageIcon(Main.class.getResource("/icons/Redo16.gif")));
	}

	public void actionPerformed(ActionEvent e) {
		//if (!myCanvas.commands.isEmpty()) {
			Command cmd = myCanvas.undoneCommands.pop();
			cmd.execute();
			myCanvas.commands.add(cmd);
			myCanvas.repaint();
		//}
            //   else
                   System.out.println();
	}
}