RecordedCommand.java

import java.util.*;
public abstract class RecordedCommand implements Command{
    public abstract void undoMe();
    public abstract void redoMe();

    private static ArrayList<RecordedCommand> undoList = new ArrayList<>();
    private static ArrayList<RecordedCommand> redoList = new ArrayList<>();

    protected static void addUndoCommand(RecordedCommand cmd){
        undoList.add(cmd);
    }

    protected static void addRedoCommand(RecordedCommand cmd){
        redoList.add(cmd);
    }

    protected static void clearRedoList(){
        redoList.clear();
    }

    public static void undoOneCommand(){
        if(undoList.size()!=0)
            undoList.remove(undoList.size()-1).undoMe();
        else{
            System.out.println("Nothing to undo.");
        }

    }

    public static void redoOneCommand(){
        if(redoList.size()!=0)
            redoList.remove(redoList.size()-1).redoMe();
        else{
            System.out.println("Nothing to redo.");
        }
    }
}