so_67570361

       //https://stackoverflow.com/questions/67570361/how-to-identify-duplicate-records-in-a-list
       Map<Boolean, List<MyVo>> partitionBasedOnRegistered = dataList.stream()
                .collect(Collectors.partitioningBy(MyVo::isRegistered));

        List<MyVo> unregisteredBusinesses = partitionBasedOnRegistered.get(Boolean.FALSE); // here
        List<MyVo> registeredBusinesses = partitionBasedOnRegistered.get(Boolean.TRUE);

        Map<String, List<MyVo>> groupByRegistrationNumber = registeredBusinesses.stream()
                .collect(Collectors.groupingBy(MyVo::registrationNumber));

        Map<Boolean, List<List<MyVo>>> partitionBasedOnDuplicates = groupByRegistrationNumber
                .entrySet().stream()
                .collect(Collectors.partitioningBy(e -> e.getValue().size() > 1,
                        Collectors.mapping(Map.Entry::getValue, Collectors.toList())));

        List<List<MyVo>> groupedRegisteredUniqueBusiness = partitionBasedOnDuplicates.get(Boolean.FALSE); // here
        List<List<MyVo>> groupedRegisteredDuplicateBusiness = partitionBasedOnDuplicates.get(Boolean.TRUE); //here