static {
   allowedChars = StringUtil.charSet(" '+,-./:=?()");
   for (char c = 'a'; c <= 'z'; c++) {
     allowedChars.set(c);
   }
   for (char c = 'A'; c <= 'Z'; c++) {
     allowedChars.set(c);
   }
   for (char c = '0'; c <= '9'; c++) {
     allowedChars.set(c);
   }
 }