code: public void setExceptionSpaceBefore(boolean isWhite) {
      if (previousExceptionList != null && exceptionValidPrevious) {
        previousExceptionList.get(previousExceptionList.size() - 1).setWhitespaceBefore(isWhite);
      } else {
        if (exceptionList != null) {
          exceptionList.get(exceptionList.size() - 1).setWhitespaceBefore(isWhite);
        }
      }
    }
docs: Sets the attribute on the exception that determines matching of patterns
  that depends on whether there was a space before the token matching the exception
  or not.
  The same procedure is used for tokens that are valid for previous or current tokens.
  
  @param isWhite If true, the space before exception is required.