code: protected void patchUnresolvedReferences()
      {
          Iterator i = unresolvedRefs.iterator();
          while (i.hasNext())
          {
              UnresolvedReference ref = (UnresolvedReference) i.next();
              Object objToFix = ref.referencingObj.target;
              JsonObject objReferenced = reader.getObjectsRead().get(ref.refId);
  
              if (ref.index >= 0)
              {    // Fix []'s and Collections containing a forward reference.
                  if (objToFix instanceof List)
                  {   // Patch up Indexable Collections
                      List list = (List) objToFix;
                      list.set(ref.index, objReferenced.target);
                  }
                  else if (objToFix instanceof Collection)
                  {   // Add element (since it was not indexable, add it to collection)
                      Collection col = (Collection) objToFix;
                      col.add(objReferenced.target);
                  }
                  else
                  {
                      Array.set(objToFix, ref.index, objReferenced.target);        // patch array element here
                  }
              }
              else
              {    // Fix field forward reference
                  Field field = MetaUtils.getField(objToFix.getClass(), ref.field);
                  if (field != null)
                  {
                      try
                      {
                          field.set(objToFix, objReferenced.target);               // patch field here
                      }
                      catch (Exception e)
                      {
                          throw new JsonIoException("Error setting field while resolving references '" + field.getName() + "', @ref = " + ref.refId, e);
                      }
                  }
              }
  
              i.remove();
          }
      }
docs: For all fields where the value was "@ref":"n" where 'n' was the id of an object
  that had not yet been encountered in the stream, make the final substitution.