Question

正在解决问题，基本代码如下所示，从用户那里获取4个可能的输入，并根据输入的响应生成响应。但是，我需要添加一个测试来验证4个可能答案中只有1个已被输入。

我知道如何比较4个输入中的2个，但不是所有4个输入，有人可以给我一个想法吗？我宁愿自己弄清楚实际的代码，但正确方向的指针也是有益的。

所以澄清如何 - 如果输入是除了＆＃34;比尔，通告，明信片或信件＆＃34;产生错误消息X

    System.out.println("What type of Letter has been received?");
    System.out.println("Bill, Circular, Postcard or Letter");
    String Letter = kybd.nextLine();

        {
            if (Letter.equalsIgnoreCase("Bill"))  
            {
                System.out.println("Bills must be paid");
            }
            else if (Letter.equalsIgnoreCase("Circular"))
            {
                System.out.println("Circulars are thrown away");
            } 
            else if (Letter.equalsIgnoreCase("Postcard"))
            {
                System.out.println("Postcards are put on the wall");
            } 
            else if (Letter.equalsIgnoreCase("Letter"))
            {
               System.out.println("Personal letters are read and have replies written for them");
            }
        }

Answer 1

            if (Letter.equalsIgnoreCase("Bill"))  
            {
                System.out.println("Bills must be paid");
            }
            else if (Letter.equalsIgnoreCase("Circular"))
            {
                System.out.println("Circulars are thrown away");
            } 
            else if (Letter.equalsIgnoreCase("Postcard"))
            {
                System.out.println("Postcards are put on the wall");
            } 
            else if (Letter.equalsIgnoreCase("Letter"))
            {
               System.out.println("Personal letters are read and have replies written for them");
            }else{
            System.out.println("ERROR");
            }

Answer 2

你想抛出一个＆＃39;否则＆＃39;那里的条件陈述，你可能想看看try和catch块，或者简单地“扔”＆＃39;您的“其他”中的NoSuchElement例外情况＆＃39;有条件的。

查看此信息可能对您有用：

http://docs.oracle.com/javase/tutorial/essential/exceptions/throwing.html

在else语句中抛出异常很像我之前的答案，而try ... catch块几乎就是你所说的测试。所以，它看起来像这样：

try
{
  Letter != "Bill"  //not exactly how it'd look, but this is a general idea on what you'd do here 
}
catch (NoSuchElementException e)
{
   System.out.println("Not a valid input.");
}

用Java纠正用户输入

2 个答案: