Can I check a String for characters other than specific ones?

Question

I am writing a Java program that can convert an inputted Roman Numeral into a Short, and I want it to be able to recognize and ask for input again when any letter has been inputted besides a Roman Numeral (I, V, X, L, C, D, and M).

Is there a method similar to .contains(), but with the opposite function?
Or do I have to check each individual letter with some kind of loop?

Answer 1

Well of course, you need some type of filter to test against the input.

One solution could be to use a string that contains all the possible valid characters in the input and then return false if a character wasn't found in the filter.

public class HelloWorld
{
  public static boolean filter(String test, String filter) {
    for(int i = 0; i < test.length(); i++) {
        if (filter.indexOf(test.charAt(i)) == -1) {
            return false;
        }
    }
    return true;
  }
  // arguments are passed using the text field below this editor
  public static void main(String[] args)
  {
    System.out.println(filter("XDQX", "XDQ"));
  }
}