### Question:
DatasetServiceFileImpl extends EmptyNetworkEntityService<Dataset> implements DatasetService { @Override public Dataset get(@NotNull UUID key) { return datasets.get(key); } DatasetServiceFileImpl(File dataFile); @Override Dataset get(@NotNull UUID key); @Override Map<UUID, String> getTitles(Collection<UUID> keys); @Override PagingResponse<Dataset> list(@Nullable Pageable page); @Override PagingResponse<Dataset> listConstituents(UUID datasetKey, @Nullable Pageable page); @Override PagingResponse<Dataset> listConstituents(@Nullable Pageable page); @Override PagingResponse<Dataset> listByCountry(Country country, @Nullable DatasetType type, @Nullable Pageable page); @Override PagingResponse<Dataset> listByType(DatasetType type, @Nullable Pageable page); @Override List<Metadata> listMetadata(UUID datasetKey, @Nullable MetadataType type); @Override List<Network> listNetworks(UUID datasetKey); @Override Metadata getMetadata(int metadataKey); @Override void deleteMetadata(int metadataKey); @Override Metadata insertMetadata(UUID datasetKey, InputStream document); @Override InputStream getMetadataDocument(UUID datasetKey); @Override InputStream getMetadataDocument(int metadataKey); @Override PagingResponse<Dataset> listDeleted(@Nullable Pageable page); @Override PagingResponse<Dataset> listDuplicates(@Nullable Pageable page); @Override PagingResponse<Dataset> listDatasetsWithNoEndpoint(@Nullable Pageable page); @Override PagingResponse<Dataset> listByDOI(String doi, @Nullable Pageable page);  }### Answer:
@Test public void get() throws Exception { DatasetService ds = new DatasetServiceFileImpl(FileUtils.getClasspathFile("registry-datasets.txt")); UUID key = UUID.fromString("c696e5ee-9088-4d11-bdae-ab88daffab78"); assertEquals(key, ds.get(key).getKey()); System.out.println(ds.get(key).toString()); }