Java 8 Fun with filters

Utils.java Testutils.java

public class Utils {

	public static List<IArtist> cull(List<IArtist> artists, List<GenreType> include, List<GenreType> exclude) {
		List<GenreType> optExclude = Optional.ofNullable(exclude).orElse(new ArrayList<GenreType>());
		List<GenreType> optInclude = Optional.ofNullable(include).orElse(new ArrayList<GenreType>());
		return artists.stream()
				.filter(isMatch(optInclude))
				.filter(isMatch(optExclude).negate())
				.collect(Collectors.toList());
	}
	public static Predicate<IArtist> isMatch(List<GenreType> matcher) {
	   return p -> !Collections.disjoint(p.getGenreTypes(), matcher);
	}
}

public class TestCull {

	@Test
	public void testNullGenreType() {
		List<IArtist> artists = new ArrayList<>();
		artists.add(new Artist("name1", Arrays.asList(GenreType.POP, GenreType.ROCK)));
		artists.add(new Artist("name2", Arrays.asList(GenreType.POP)));
		artists.add(new Artist("name3", Arrays.asList(GenreType.RAP)));
		//artists.add(new Artist("name4"));
		
		//System.out.println(artists.get(3).getGenreTypes().contains(GenreType.RAP));
		List<GenreType> include = new ArrayList<>();
		include.add(GenreType.POP);
		
		List<IArtist> culled = Utils.cull(artists, include, null	);
		assertEquals(2, culled.size());
		assertEquals("name1", culled.get(0).getName());
		assertEquals("name2", culled.get(1).getName());	
	}
	@Test
	public void testIncludeOnly() {
		List<IArtist> artists = new ArrayList<>();
		artists.add(new Artist("name1", Arrays.asList(GenreType.POP, GenreType.ROCK)));
		artists.add(new Artist("name2", Arrays.asList(GenreType.POP)));
		artists.add(new Artist("name3", Arrays.asList(GenreType.RAP)));
		//artists.add(new Artist("name4"));
		
		//System.out.println(artists.get(3).getGenreTypes().contains(GenreType.RAP));
		List<GenreType> include = new ArrayList<>();
		include.add(GenreType.POP);
		List<GenreType> exclude = new ArrayList<>();
		
		List<IArtist> culled = Utils.cull(artists, include, exclude);
		assertEquals(2, culled.size());
		assertEquals("name1", culled.get(0).getName());
		assertEquals("name2", culled.get(1).getName());	
	}
	@Test
	public void testIncludeAndExcludeOnly() {
		List<IArtist> artists = new ArrayList<>();
		artists.add(new Artist("name1", Arrays.asList(GenreType.POP, GenreType.ROCK)));
		artists.add(new Artist("name2", Arrays.asList(GenreType.POP, GenreType.RAP)));
		artists.add(new Artist("name3", Arrays.asList(GenreType.RAP)));
		
		List<GenreType> include = new ArrayList<>();
		include.add(GenreType.POP);
		
		List<GenreType> exclude = new ArrayList<>();
		exclude.add(GenreType.RAP);
		
		List<IArtist> culled = Utils.cull(artists, include, exclude);
		assertEquals(1, culled.size());
		assertEquals("name1", culled.get(0).getName());
	}
	@Test
	public void excludeOnly() {
		List<IArtist> artists = new ArrayList<>();
		artists.add(new Artist("name1", Arrays.asList(GenreType.POP, GenreType.ROCK)));
		artists.add(new Artist("name2", Arrays.asList(GenreType.POP, GenreType.RAP)));
		artists.add(new Artist("name3", Arrays.asList(GenreType.RAP)));
		
		List<GenreType> include = new ArrayList<>();
		
		List<GenreType> exclude = new ArrayList<>();
		exclude.add(GenreType.RAP);
		
		List<IArtist> culled = Utils.cull(artists, include, exclude);
		assertEquals(0, culled.size());
	}
}