Question

just to clarify this is hw.

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;
}

The error is on

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

Eclipse says

invalid character constant 

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

i.e. case ‘1’: case ‘2’:

even with

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

It won’t work.

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

Thank you!

Answer 1

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':

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.

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")
}