code: void showWarnings(SQLWarning warn) {
      if (warn == null) {
        return;
      }
  
      if (seenWarnings.get(warn) == null) {
        // don't re-display warnings we have already seen
        seenWarnings.put(warn, new java.util.Date());
        handleSQLException(warn);
      }
  
      SQLWarning next = warn.getNextWarning();
      if (next != warn) {
        showWarnings(next);
      }
    }
docs: Print the specified warning on the console, as well as any warnings that
  are returned from {@link SQLWarning#getNextWarning}.
  
  @param warn the {@link SQLWarning} to print