HashMap<String, List<ResourceRelationshipCharacteristicDTO>> hashMap = new HashMap<>();

        List<ResourceRelationshipDTO> rrsDTIO = resources.stream().flatMap(e -> e.getRelationshipDTO().stream()).collect(Collectors.toList());
        rrsDTIO.forEach(e -> {
                    if (hashMap.containsKey(e.getResourceRefDTO().get().getId().get()))
                        hashMap.put(e.getResourceRefDTO().get().getId().get(), e.getResourceRelationshipCharacteristicDTO()
                                .stream().filter(f -> "Device".equals(f.getValue())).collect(Collectors.toList())
                        );
                }
        );