code: protected int storeReference(Object obj) {
          int newRefId = refId.getAndIncrement();
          //log.trace("storeReference - ref id: {} obj: {}", newRefId, obj);
          refMap.put(Integer.valueOf(newRefId), obj);
          return newRefId;
      }
docs: Store an object into a map.
  
  @param obj
  Object to store
  @return reference id