ex3

hw2/.idea/.gitignore

@@ -0,0 +1,8 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml

hw2/.idea/hw2.iml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$" />
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

hw2/.idea/modules.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/.idea/hw2.iml" filepath="$PROJECT_DIR$/.idea/hw2.iml" />
+    </modules>
+  </component>
+</project>

hw2/.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$/.." vcs="Git" />
+  </component>
+</project>

hw3/code/Assignment3.iml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module org.jetbrains.idea.maven.project.MavenProjectsManager.isMavenModule="true" type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_17">
+    <output url="file://$MODULE_DIR$/target/classes" />
+    <output-test url="file://$MODULE_DIR$/target/test-classes" />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src/main/java" isTestSource="false" />
+      <excludeFolder url="file://$MODULE_DIR$/target" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

hw3/code/src/main/java/ch/usi/inf/ajp22/Album.java

@@ -3,6 +3,7 @@ package ch.usi.inf.ajp22;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Optional;
+import java.util.stream.Collectors;
 
 public class Album {
 
@@ -44,19 +45,30 @@ public class Album {
 
     /**
      * 3 Points
-     * TODO: create a public Optional<Track> method called "searchLongestSong" that
-     *       return the longest Track in the album.
+     *      create a public Optional<Track> method called "searchLongestSong" that
+     *       return the longest Track on the album.
      *       input: void
      *       output: an Optional<Track>
      */
+    public Optional<Track> searchLongestSong() {
+        return this.tracks.stream()
+                .max(Comparator.comparingInt(Track::getLength));
+    }
 
     /**
      * 3 Points
-     * TODO: create a public List<Track> method called "orderSongByTitle" that
+     *      create a public List<Track> method called "orderSongByTitle" that
      *       return the track list ordered lexicographically using the title field.
      *       input: void
      *       output: a List<Track>
      */
+    public List<Track> orderSongByTitle() {
+        // note: we assume lexicographical order requires letter case to be ignored
+        return this.tracks.stream()
+                .sorted((a, b) -> String.CASE_INSENSITIVE_ORDER.compare(a.getTitle(), b.getTitle()))
+                .collect(Collectors.toList());
+    }
+
 
     @Override
     public String toString() {

hw3/code/src/main/java/ch/usi/inf/ajp22/Main.java

@@ -5,107 +5,154 @@ import java.io.FileWriter;
 import java.io.IOException;
 import java.time.LocalDate;
 import java.util.*;
-import java.util.function.BiFunction;
-import java.util.function.BinaryOperator;
-import java.util.function.IntFunction;
-import java.util.function.Predicate;
+import java.util.function.*;
 import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 import java.util.stream.Stream;
 
 public class Main {
 
     /**
      * 3 Points
-     * TODO: create a public static Album method called "longestTitle".
+     * create a public static Album method called "longestTitle".
      * If the maximum is not found throw a RuntimeException.
      * input: a list of Album
      * output: the Album with the longest title.
      */
 
+    public static Album longestTitle(List<? extends Album> albums) {
+        return albums.stream()
+                .max(Comparator.comparingDouble(a -> a.getTitle().length()))
+                .orElseThrow(RuntimeException::new);
+    }
+
     /**
      * 4 Points
-     * TODO: create a public static int method called "sumOfRatingReduce".
+     * create a public static int method called "sumOfRatingReduce".
      * input: an Album instance.
-     *       output: int that is the sum of all the tracks ratings in the album.
+     * output: int that is the sum of all the tracks ratings on the album.
      * Use the method getTracks from the Album class to get the List of tracks.
      * You MUST use the reduce method, in the variant which takes as input an identity, an accumulator and a combiner.
      * If possible use method references.
      */
+    public static int sumOfRatingReduce(Album album) {
+        return album.getTracks().stream()
+                .map(Track::getLength)
+                .reduce(0, Integer::sum, Integer::sum);
+    }
 
     /**
      * 4 Points
-     * TODO: create a public static int method called "sumOfRatingCollection".
+     * create a public static int method called "sumOfRatingCollection".
      * input: an Album instance.
-     *       output: int that is the sum of all the tracks ratings in the album
+     * output: int that is the sum of all the tracks ratings on the album
      * Use the method getTracks from the Album class to get the List of tracks.
      * You MUST use one variant of the collect method. If possible use method references.
      */
+    public static int sumOfRatingCollection(Album album) {
+        //noinspection SimplifyStreamApiCallChains
+        return album.getTracks().stream().map(Track::getRating)
+                .collect(Collectors.reducing(0, Integer::sum));
+    }
+
 
     /**
      * 4 Points
-     * TODO: create a public static int method called "sumOfRatingMap"
-     *       input: an ch.usi.inf.ajp22.Album instance.
-     *       output: int that is the sum of all the tracks ratings in the album.
+     * create a public static int method called "sumOfRatingMap"
+     * input: a ch.usi.inf.ajp22.Album instance.
+     * output: int that is the sum of all the tracks ratings on the album.
      * Use the method getTracks from the Album class to get the List of tracks.
      * You MUST use the mapToInt method. If possible use method references.
      */
+    public static int sumOfRatingMap(Album album) {
+        return album.getTracks().stream().mapToInt(Track::getRating).sum();
+    }
 
     /**
      * 4 Points
-     * TODO: create a public static Map<String, Long> method called "countTrackOccurrence"
+     * create a public static Map<String, Long> method called "countTrackOccurrence"
      * input: a list of Track
      * output: a Map<String, Long> where the key is the track title and the value is, how many times
      * the same song occurs in the list.
      * Two songs can be considered the same if they have the same title.
      */
+    public static Map<String, Long> countTrackOccurrence(List<? extends Track> tracks) {
+        return tracks.stream().collect(Collectors.groupingBy(Track::getTitle, Collectors.counting()));
+    }
 
     /**
      * 4 Points
-     * TODO: create a public static Map<Artist, List<Album>> method called "groupAlbumByArtist".
+     * create a public static Map<Artist, List<Album>> method called "groupAlbumByArtist".
      * input: a list of Album
      * output: a Map<Artist, List<Album>> where the key is an Artist and the value is a List of Album which
      * this artist had produced.
      */
+    public static Map<Artist, List<Album>> groupAlbumByArtist(List<? extends Album> albums) {
+        return albums.stream().collect(Collectors.groupingBy(Album::getArtist, Collectors.toList()));
+    }
 
     /**
      * 4 Points
-     * TODO: create a public static List<Track> method called "trackFilteredWithPredicate".
+     * create a public static List<Track> method called "trackFilteredWithPredicate".
      * input: a stream of tracks and a predicate to apply to the track stream.
      * output: a List of Track that has been filtered according to the predicate taken as input.
      */
+    public static List<Track> trackFilteredWithPredicate(Stream<? extends Track> tracks, Predicate<? super Track> predicate) {
+        return tracks.filter(predicate).collect(Collectors.toList());
+    }
 
     /**
      * 5 Points
-     * TODO: create a public static Stream<Album> method called getAlbumWithAtLeastNTracks
+     * create a public static Stream<Album> method called getAlbumWithAtLeastNTracks
      * input: a list of Album AND an int called "n"
      * output: a List<Album> where every album in this stream has at least "n" tracks.
      */
+    public static Stream<Album> getAlbumWithAtLeastNTracks(List<Album> albums, int n) {
+        return albums.stream().filter(a -> a.getTracks().size() >= n);
+    }
 
     /**
      * 5 Points
-     * TODO: create a public static void method called "printTrackStatistics".
+     * create a public static void method called "printTrackStatistics".
      * input: an Album instance
      * Print Track Statistics based on the length of the tracks of an album taken as input in the following format:
      * ===
-     * "Stat for: %s\n", album.getTitle())
+     * "Stat for: %s\n", album.getTitle()
      * "Max: %d\nMin: %d\nAve: %f\n"
      * ===
      * Use the method getTracks from the Album class to get the List of tracks.
      * Input: an Album
      */
+    public static void printTrackStatistics(Album album) {
+        final Supplier<IntStream> tracksStreamSupplier = () -> album.getTracks().stream().mapToInt(Track::getLength);
+        final Supplier<IllegalArgumentException> whenZero = () -> {
+            throw new IllegalArgumentException("Album has no tracks");
+        };
+
+        System.out.printf("===\nStat for: %s\nMax: %d\nMin: %d\nAve: %f\n===\n",
+                album.getTitle(),
+                tracksStreamSupplier.get().max().orElseThrow(whenZero),
+                tracksStreamSupplier.get().min().orElseThrow(whenZero),
+                tracksStreamSupplier.get().average().orElseThrow(whenZero));
+    }
 
     /**
      * 5 Points
-     * TODO: create a public static String method called "getArtistNameAndNickNameFromAlbum".
+     * create a public static String method called "getArtistNameAndNickNameFromAlbum".
      * Each author should appear only once.
      * input: a list of Album
      * output: a String in the following format:
      * [artist1.name - artist1.nickname, artist2.name - artist2.nickname, ...]
      */
+    public static String getArtistNameAndNickNameFromAlbum(List<? extends Album> albums) {
+        return albums.stream().map(Album::getArtist).distinct()
+                .map(a -> String.format("%s - %s", a.getName(), a.getNickname()))
+                .collect(Collectors.joining(",", "[", "]"));
+    }
 
     /**
      * 5 Points
-     * TODO: create a public Track method called "combineAllTrackInAlbum"
+     * create a public Track method called "combineAllTrackInAlbum"
      * input: a stream of track
      * output: return a new ch.usi.inf.ajp22.Track with the following values:
      * title -> "fake title"
@@ -116,25 +163,39 @@ public class Main {
      * You MUST use the collect method, in the variant which takes as input a supplier, an accumulator and a
      * combiner.
      */
+    public static Track combineAllTrackInAlbum(Stream<? extends Track> tracks) {
+        return tracks.parallel().collect(
+                () -> new Track("fake title", LocalDate.now(), Track.Genre.DISCO, 0),
+                (acc, track) -> acc.setLength(acc.getLength() + track.getLength()),
+                (acc, other) -> acc.setLength(acc.getLength() + other.getLength()));
+    }
 
     /**
      * 5 Points
-     * TODO: create a public static Map<Artist, List<Track>> method called "groupTrackByArtist".
+     * create a public static Map<Artist, List<Track>> method called "groupTrackByArtist".
      * input: a list of Album
      * output: a Map<Artist, List<Track>> where the key is an Artist and the value is a List of Track which
      * this artist had produced.
      */
+    public static Map<Artist, List<Track>> groupTrackByArtist(List<? extends Album> albums) {
+        return albums.stream().collect(
+                Collectors.groupingBy(
+                        Album::getArtist,
+                        Collectors.flatMapping(a -> a.getTracks().stream(), Collectors.toList())));
+    }
 
     /**
      * 5 Bonus Points
-     * TODO: create a public static <T> T[] method called "createArray".
+     * create a public static <T> T[] method called "createArray".
      * This method must create a generic array where the elements are in the same order as in the
      * input Collection.
      * In this function you need neither streams nor lambda.
      * input: a Collection<T> and an IntFunction<T[]>
      * output: an array of generic type
      */
-
+    public static <T> T[] createArray(Collection<T> collection, IntFunction<T[]> generator) {
+        return collection.toArray(generator);
+    }
 
     private static void writeToFile(String s) throws IOException {
         BufferedWriter fw = new BufferedWriter(new FileWriter("artist.txt", true));
@@ -145,7 +206,7 @@ public class Main {
     public static void main(String[] args) {
         Random random = new Random();
 
-        /**
+        /*
          * Initializing some SampleData
          */
         SampleData.appetiteForDestruction
@@ -156,35 +217,40 @@ public class Main {
                 .getTracks().forEach(track ->
                         track.setRating(random.nextInt(5)));
 
-        /**
+        /*
          * 2 Points
-         * TODO: Replace the Anonymous class below with a lambda expression.
+         *       Replace the Anonymous class below with a lambda expression.
          */
-        BinaryOperator<Track> mixTrack = new BinaryOperator<>() {
-            @Override
-            public Track apply(Track t1, Track t2) {
-                return new Track(t1.getTitle(),
+        BinaryOperator<Track> mixTrack = (t1, t2) -> new Track(t1.getTitle(),
                 t1.getReleasedDate(),
                 t2.getGenre(),
                 t2.getLength());
-            }
-        };
 
-        /**
+        /*
          * 3 Points
-         * TODO: Create a stream pipeline that:
+         *       Create a stream pipeline that:
          *       1) filter all the tracks that have at least 4 as rating
          *       2) sort the filtered tracks using the title field
          *       3) print the tracks
          */
+        SampleData.getShuffledTrack().stream().filter(t -> t.getRating() >= 4)
+                .sorted(Comparator.comparing(Track::getTitle))
+                .forEach(System.out::println);
 
-        /**
+        /*
          * 4 Points
-         * TODO: Print on file the artist's name, obtained with the method SampleData.getArtistList(),
+         *       Print on file the artist's name, obtained with the method SampleData.getArtistList(),
          *       using the writeToFile method. Use a lambda expression and handle
          *       the throw exception from the writeToFile method. If there is an IOException you must throw a
          *       RuntimeException with the same event.
          */
+        SampleData.getArtistList().stream().map(Artist::getName).forEach(n -> {
+            try {
+                writeToFile(n);
+            } catch (final IOException e) {
+                throw new RuntimeException(e);
+            }
+        });
 
         System.out.printf("Longest track in %s is %s\n",
                 SampleData.appetiteForDestruction.getTitle(),
@@ -229,13 +295,13 @@ public class Main {
         Map<Artist, List<Track>> artistListMap1 = groupTrackByArtist(SampleData.getAlbumList());
         for (Map.Entry<Artist, List<Track>> entry : artistListMap1.entrySet()) {
             System.out.println("ch.usi.inf.ajp22.Artist: " + entry.getKey().getName());
-            for (Track track: entry.getValue()) {
+            for (Track track : entry.getValue()) {
                 System.out.println("\t" + track.toString());
             }
         }
 
         List<Track> trackPOPinGuns = trackFilteredWithPredicate(SampleData.appetiteForDestruction.getTracks().stream()
-                ,(t -> !t.getGenre().equals(Track.Genre.HIP_HOP)));
+                , (t -> !t.getGenre().equals(Track.Genre.HIP_HOP)));
         trackPOPinGuns
                 .forEach(System.out::println);