code: @Override
    @SuppressWarnings({"unchecked", "deprecated"})
    public <U> ComposableFuture<U> continueOnSuccess(final SuccessHandler<? super T, ? extends U> handler) {
      return map(result -> {
        try {
          return handler.handle(result);
        } catch (final ExecutionException e) {
          // new API doesn't allows checked exceptions - offering throwing runtime instead. sadly, doing this for BC.
          throw new UncheckedExecutionException(e.getCause());
        }
      });
    }
docs: /*
  OLD API - DEPRECATED