switch语句中有多个字符? [英] Multiple characters in a switch statement?

问题描述

只是为了澄清这是硬件.

just to clarify this is hw.

在我们正在执行的项目中，不允许用户输入数字或特殊字符(即！@£等)

In a project we're doing, a user isn't allowed to enter numbers or special characters (i.e ! @ £ etc)

        char letter;
        String phonetic;

        Scanner kb = new Scanner(System.in);


        System.out.print("Please enter a letter: ");
        letter = letter = kb.next().charAt(0);

        switch(Character.toUpperCase(letter))
{
       case 'A':
            {
                Dot();
                Dash();
                Red();
            }
            break;

        case '1,2,3,4,5,6,7,8,9,0':
            {
               System.out.println('No number input please!');
            }
        break;
}

错误在

'1,2,3,4,5,6,7,8,9,0' 

Eclipse说

invalid character constant 

如果我必须手动输入所有数字，这真的很麻烦吗?

Isn't it really long winded if I have to enter all the numbers manually?

即情况'1':情况'2':

i.e. case '1': case '2':

即使

case 1,2,3,4,5,6,7,8,9,0: 

这行不通.

是否有使用switch语句执行此操作的更短方法?

Is there an shorter way to do this using switch statements?

谢谢！

推荐答案

这是因为Case表达式应该是 java 7 中的int-compatible literal或String.

Its because Case expression should be an int-compatible literal or a String from java 7.

case '1,2,3,4,5,6,7,8,9,0':

字符文字用单引号表示. c，它只能是一个长度，而您的情况不能反映这一点，因此是错误.

character literals are represented using single quotes. c, it should only be of one length, while your case doesn't reflect that, thus the error.

'1,2,3,4,5,6,7,8,9,0'  this is not a legal character.

如果您只是想检查字符是否仅是字母，请使用

If you just wanna check if the character is only alpha, then use Charcter#isDigit(char) or Charcter#isLetter before the switch starts like in below code:

char ch=  (Character.toUpperCase(letter);
if(!Character.isDigit(ch)) {
    switch(Character.toUpperCase(letter))
     {
       case 'A':
            {
                Dot();
                Dash();
                Red();
            }
            break;
        }
     }
else {
       System.out.println("no numbers please")
}

这篇关于switch语句中有多个字符?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！