code: public List<ResourceRequest> getResourcesToRelease() {
      List<ResourceRequest> release = new ArrayList<ResourceRequest>();
      synchronized(lockObject) {
        for (Integer requestId:
          setDifference(requestedResources.keySet(), requestMap.keySet())) {
          // We update the data structures right away. This assumes that the
          // caller will be able to release the resources.
          ResourceRequest req = requestedResources.remove(requestId);
          if (req != null) {
            release.add(req);
            LOG.info("Filing release for requestId: " + req.getId());
          }
        }
      }
      return release;
    }
docs: Go through all the requested resources and find what needs to be released.
  @return