undo/redo

   /** @param command */
   public void executeCommand(Command command) {
      // TODO: implement
       for(int i = commands.size() -1; i > currentCommandIndex; i--){
           commands.remove(i); // praznjenje redo liste
       }
       commands.add(command);
       command.execute();
       currentCommandIndex++;
   }

   public void undo() {
      // TODO: implement
       if(currentCommandIndex > -1){
           Command currentCommandToUndo = commands.get(currentCommandIndex);
           currentCommandToUndo.undo();
           currentCommandIndex--;
       }
   }

   public void redo() {
      // TODO: implement
       if(currentCommandIndex < commands.size() -1){
           Command currentCommandToRedo = commands.get(currentCommandIndex + 1);
           currentCommandToRedo.execute();
           currentCommandIndex++;
       }
   }