code: public static void checkSyntax(String fqan) {
  
      if (fqan.length() > 255)
        throw new VOMSError("fqan.length() > 255");
  
      if (!fqanPattern.matcher(fqan).matches())
        throw new VOMSError("Syntax error in fqan: " + fqan);
    }
docs: This methods checks that the string passed as argument complies with the
  voms FQAN syntax.
  
  @param fqan
  the string that must be checked for compatibility with FQAN
  syntax.
  @throws VOMSError
  If there's an error in the FQAN syntax.