code: public void  printKeys () {
      java.util.Set<Map.Entry<Enum, String>> task = this._task.entrySet();
      int size = task.size();
      java.util.Iterator<Map.Entry<Enum, String>> kv = task.iterator();
      for (int i = 0; i < size; i++)
      {
        Map.Entry<Enum, String> entry = (Map.Entry<Enum, String>) kv.next();
        Enum key = entry.getKey();
        String value = entry.getValue();
        System.out.println("Key:<" + key.name() + ">, value:<"+ value +">"); 
      }
    }
docs: /*
  Print the key/values pairs for a task