code: public static void addSuppressed(Throwable t, Throwable suppressed) {
      if (METHOD_ADD_SUPPRESSED != null) {
        try {
          METHOD_ADD_SUPPRESSED.invoke(t, suppressed);
        }
        catch (Exception e) {
          throw new IllegalStateException("Could not add suppressed exception:", e);
        }
      }
    }
docs: If supported. appends the specified exception to the exceptions that were suppressed in order to deliver this exception.