code: public final void validate(StringBuilder source) {
  
      int length = source.length();
      source.append('/');
      source.append(getSourceIdentifier());
      doValidate(source);
      // reset source for recursive invocation...
      source.setLength(length);
    }
docs: This method validates this segment recursively to ensure the correctness of the configured format.
  
  @param source describes the source of the validation.