How to validate a Greek Tax Number (AFM)

gistfile1.java

// From http://www.gsis.gr/gsis/info/gsis_site/Services/Polites/sources.html
// gr.gsis.e7.E7File class
// Apache 2.0 license

  public static boolean afmIsValid(String afm) {
    int sum = 0;

    if (afm.length() != 9)
      return false;
    for (int i = 0; i < 8; i++)
      sum += (afm.charAt(i) - '0') << (8 - i);
    return ((afm.charAt(8) - '0') == ((sum % 11) % 10));
  }