[Q#15150193][A#15150223] How to check that a string contains characters other than those specified. (in Java)

https://stackoverflow.com/q/15150193

I have a program that asks the user to input a three character string. The string can only be a combination of a, b, or c. How do I check if the string contains any other characters than those specified without doing a million conditional statements. Pseudo example:

Answer

https://stackoverflow.com/a/15150223

To look for characters that are NOT a, b, or c, use something like the following:

APIzation

if(!s.matches("[abc]+"))
{
    System.out.println("The string you entered has some incorrect characters");
}

package com.stackoverflow.api;

public class Human15150223 {

  public static boolean stringMatchesCharactersExclusively(
    String s,
    String characters
  ) {
    //https://stackoverflow.com/a/15150223
    if (!s.matches("[" + characters + "]+")) {
      System.out.println(
        "The string you entered has some incorrect characters"
      );
      return false;
    }

    return true;
  }
}

package com.stackoverflow.api;

/**
 * How to check that a string contains characters other than those specified. (in Java)
 *
 * @author APIzator
 * @see <a href="https://stackoverflow.com/a/15150223">https://stackoverflow.com/a/15150223</a>
 */
public class APIzator15150223 {

  public static void check(String s) throws Exception {
    if (!s.matches("[abc]+")) {
      System.out.println(
        "The string you entered has some incorrect characters"
      );
    }
  }
}