开关不兼容类型错误

Question

I'm writing a roman numeral program for my class. I'm using a switch statement to convert strings to integers. However I'm getting an incompatible type error when I run it. Im running java 7 so that's not the issue. Here's my code:

public static void main()
{
    // Declare local variables
    Scanner input = new Scanner(System.in);
    String rNum;
    int i;
    int[] rArray;

    // Display program purpose
    System.out.println("This Program Converts Roman numerals to decimals");
    System.out.println("The Roman numerals are I (1), V (5), X (10), L (50), C (100), D (500) and M (1000).");
    System.out.print("Enter your roman numeral: ");

    rNum = input.next().toUpperCase();

    rArray = new int[rNum.length()];

    for(i = 0; i < rNum.length(); i++){
      switch(rNum.charAt(i)){
          case "I": rArray[i] = 1;
          break;
      }
      }

Answer 1

"I" is a one character String. 'I' is the character I, type char , which is what you need in your case block.

Answer 2

您正在尝试将char （在switch （）中）与String （在您的case块中）匹配，这是无效的

Answer 3

The Switch statement contains a character variable, where as your case refers to string. You need to decide, you want to use string or char and maintain the uniformity throughout.

Here is the code that fixes the above issue.

class test {
    public static void main(){
        // Declare local variables
        Scanner input = new Scanner(System.in);
        String rNum;
        int i;
        int[] rArray;

        // Display program purpose
        System.out.println("This Program Converts Roman numerals to decimals");
        System.out.println("The Roman numerals are I (1), V (5), X (10), L (50), C (100), D (500) and M (1000).");
        System.out.print("Enter your roman numeral: ");

        rNum = input.next().toUpperCase();
        rArray = new int[rNum.length()];

        for(i = 0; i < rNum.length(); i++){
            switch(rNum.charAt(i)){
            case 'I': rArray[i] = 1;
            break;

            case 'V': rArray[i] = 1;
            break;

            case 'X': rArray[i] = 1;
            break;

            case 'L': rArray[i] = 1;
            break;

            //Continue in the same manner as above.
            //Not sure, if this is the right way to convert and will
            //convert all types of number. Just check on this.
            }
        }

    }
}