package class8_3_PhonebookCommands_start;//package pbook;

public abstract class Command {
   protected PhoneBook pb; // phonebook to modify

   public Command(PhoneBook pb) {
      this.pb = pb;
   }

   public PhoneBook book() { return pb; }
   
   public abstract void execute(); // executing the command

   public abstract void unexecute(); // undoing the command
}