if(aliasValue.length() != 0 && aliasValue.length() <= 100) {
   alias = aliasValue.toLowerCase();

   for(i = 0; i < alias.length() && "0123456789abcdefghijklmnopqrstuvwxyz".indexOf(alias.charAt(i)) >= 0; ++i) {;}

   if(i != alias.length()) {
      responses.put("errorCode", Integer.valueOf(4));
      responses.put("errorDescription", "Incorrect \"alias\" (must contain only digits and latin letters)");
   } else {
      uri = uri.trim();
      if(uri.length() > 1000) {
         responses.put("errorCode", Integer.valueOf(4));
         responses.put("errorDescription", "Incorrect \"uri\" (length must be not longer than 1000 characters)");
      } else {
...
} else {
   responses.put("errorCode", Integer.valueOf(4));
   responses.put("errorDescription", "Incorrect \"alias\" (length must be in [1..100] range)");
}