HashSet<Integer> hashSet = new HashSet<Integer>();

         for (int i = resultDoctorDetails.size() - 1; i >= 0; --i) {

             ResultDoctorDetail temp = resultDoctorDetails.get(i);

             if (!hashSet.contains(temp.getUserId())) {

                 hashSet.add(temp.getUserId());

             } else {

                 resultDoctorDetails.remove(i);

             }

         }