如何重新提示用户输入答案？

Question

如果我转而使用while语句，我将如何得到提示将其恢复到序列的开头？

 if (al.contains(room)) {
      System.out.println("Entered "+room);
    }
 else {
     System.err.println("I couldnt get that, please type exactly which room you want to enter:  ");
 }