code: public T marketplace_getListings(Collection<Long> listingIds, Collection<Integer> userIds)
      throws FacebookException, IOException {
  
      ArrayList<Pair<String, CharSequence>> params =
        new ArrayList<Pair<String, CharSequence>>(FacebookMethod.MARKETPLACE_GET_LISTINGS.numParams());
      if (null != listingIds && !listingIds.isEmpty()) {
        params.add(new Pair<String, CharSequence>("listing_ids", delimit(listingIds)));
      }
      if (null != userIds && !userIds.isEmpty()) {
        params.add(new Pair<String, CharSequence>("uids", delimit(userIds)));
      }
  
      assert !params.isEmpty() : "Either listingIds or userIds should be provided";
      return this.callMethod(FacebookMethod.MARKETPLACE_GET_LISTINGS, params);
    }
docs: Fetch marketplace listings, filtered by listing IDs and/or the posting users' IDs.
  @param listingIds listing identifiers (required if uids is null/empty)
  @param userIds posting user identifiers (required if listingIds is null/empty)
  @return a T of marketplace listings
  @see <a href="http://wiki.developers.facebook.com/index.php/Marketplace.getListings">
  Developers Wiki: marketplace.getListings</a>