[Ch10c] Trying to make sense of the queries we have, and what would be useful for the book (90995626) · Commits · examples / Head First Java 3rd Edition

src/test/java/ch10c/JukeboxQueriesTest.java

+70 −2

Changes for src/test/java/ch10c/JukeboxQueriesTest.java: 70 added lines, 2 removed lines.
Original line number	Diff line number	Diff line
		@@ -24,6 +24,7 @@ class JukeboxQueriesTest {
		System.out.println(allSongs);
		}

		// Sorting, Collect to List
		@Test
		void shouldOrderByLeastPlayed() {
		List<Song> allSongs = songs.getSongs();
		@@ -39,20 +40,29 @@ class JukeboxQueriesTest {
		void shouldQueryForGenre() {
		List<Song> allSongs = songs.getSongs();
		// ORDER MATTERS
		List<String> genres = allSongs.stream().map(song -> song.getGenre())
		// find all genres in played music
		List<String> genres = allSongs.stream()
		.map(song -> song.getGenre())
		.distinct()
		.collect(toList());
		System.out.println("genres = " + genres);

		System.out.println(allSongs.stream().map(song -> song.getGenre())
		// find number of distinct genres
		System.out.println(allSongs.stream()
		.map(song -> song.getGenre())
		.distinct()
		.count());

		// find number songs for each genre
		// GROUPING
		Map<String, Long> genreCount = allSongs.stream().map(song -> song.getGenre())
		.collect(groupingBy(Function.identity(), counting()));
		System.out.println("genreCount = " + genreCount);
		}

		// OPTIONAL
		// max terminal
		// Comparator
		@Test
		void shouldFindMostPopularSong() {
		List<Song> allSongs = songs.getSongs();
		@@ -82,6 +92,9 @@ class JukeboxQueriesTest {
		System.out.println("result = " + genreCount);
		}

		// STRAIGHTFORWARD
		// filter
		// toList
		@Test
		void shouldFindHowManySongsAreSomeSortOfRock() {
		List<Song> allSongs = songs.getSongs();
		@@ -93,6 +106,7 @@ class JukeboxQueriesTest {
		System.out.println(result);
		}

		// GROUPING
		@Test
		void shouldFindNumberOfTimesSongTitleAppears() {
		List<Song> allSongs = songs.getSongs();
		@@ -103,4 +117,58 @@ class JukeboxQueriesTest {

		System.out.println("result = " + result);
		}

		// STRAIGHTFORWARD
		// min terminal
		// OPTIONAL
		@Test
		void shouldGetOldestSong() {
		List<Song> allSongs = songs.getSongs();
		Optional<Song> result = allSongs.stream()
		.min(Comparator.comparingInt(Song::getYear));

		System.out.println("result = " + result.get());
		}

		// STRAIGHTFORWARD
		// filter (with param)
		// toList
		@Test
		void shouldBeAbleToFindAllVersionsOfASong() {
		List<Song> allSongs = songs.getSongs();

		String songTitle = "Hurt";
		List<Song> result = allSongs.stream()
		.filter(song -> song.getTitle().equals(songTitle))
		.collect(toList());

		System.out.println("result = " + result);
		}

		@Test
		void shouldFilterMapCollect() {
		List<Song> allSongs = songs.getSongs();

		String songTitle = "With a Little Help from My Friends";
		List<String> result = allSongs.stream()
		.filter(song -> song.getTitle().equals(songTitle))
		.map(Song::getArtist)
		.collect(toList());

		System.out.println("result = " + result);
		}

		// PRIMITIVE STREAMS
		@Test
		void shouldBeAbleToCalculateCountForAllVersionsOfASong() {
		List<Song> allSongs = songs.getSongs();

		String songTitle = "Hurt";
		int result = allSongs.stream()
		.filter(song -> song.getTitle().equals(songTitle))
		.mapToInt(Song::getTimesPlayed)
		.sum();

		System.out.println("result = " + result);
		}
		}
		No newline at end of file