Implement Composite Design Pattern

Design Patterns/src/composite/Main.java

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+package composite;
+
+public class Main {
+    public static void main(String[] args){
+
+        SongComponent musicFolder = new SongGroup("Goudham's Music Folder", "- A personal collection of songs that I enjoy");
+
+        SongComponent kpopMusic =
+                new SongGroup("Kpop",
+                        "is a genre of popular music originating in South Korea.");
+
+        SongComponent electronicMusic =
+                new SongGroup("\nElectronic",
+                        "is music that employs electronic musical instruments, digital instruments or circuitry-based music technology");
+
+        SongComponent jpopMusic =
+                new SongGroup("\nJpop",
+                        "is a musical genre that entered the musical mainstream of Japan in the 1990s");
+
+        musicFolder.add(kpopMusic);
+
+        kpopMusic.add(new Song("Better", "Twice", 2020));
+        kpopMusic.add(new Song("Deja Vu", "Dreamcatcher", 2019));
+
+        musicFolder.add(jpopMusic);
+
+        jpopMusic.add(new Song("PA PA YA", "BabyMetal", 2019));
+        jpopMusic.add(new Song("Megitsune", "BabyMetal", 2013));
+
+        musicFolder.add(electronicMusic);
+
+        electronicMusic.add(new Song("Houndin", "Layto", 2020));
+        electronicMusic.add(new Song("Wrong", "Far Out", 2017));
+
+        musicFolder.displaySongInfo();
+    }
+}

Design Patterns/src/composite/Song.java

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+package composite;
+
+public class Song extends SongComponent {
+
+    String songName;
+    String bandName;
+    int releaseYear;
+
+    public Song(String songName, String bandName, int releaseYear){
+        this.songName = songName;
+        this.bandName = bandName;
+        this.releaseYear = releaseYear;
+    }
+
+    @Override
+    public String getSongName() { return songName; }
+
+    @Override
+    public String getBandName() { return bandName; }
+
+    @Override
+    public int getReleaseYear() { return releaseYear; }
+
+    @Override
+    public void displaySongInfo(){ System.out.println(this); }
+
+    @Override
+    public String toString() {
+        return "Song{" +
+                "songName='" + songName + '\'' +
+                ", bandName='" + bandName + '\'' +
+                ", releaseYear=" + releaseYear +
+                "} ";
+    }
+}

Design Patterns/src/composite/SongComponent.java

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+package composite;
+
+public abstract class SongComponent {
+
+    public void add(SongComponent songComponent) {
+        throw new UnsupportedOperationException();
+    }
+
+    public void remove(SongComponent songComponent) {
+        throw new UnsupportedOperationException();
+    }
+
+    public SongComponent getComponent(int componentIndex) { throw new UnsupportedOperationException(); }
+
+    public String getSongName() { throw new UnsupportedOperationException(); }
+
+    public String getBandName() { throw new UnsupportedOperationException(); }
+
+    public int getReleaseYear() { throw new UnsupportedOperationException(); }
+
+    public void displaySongInfo() { throw new UnsupportedOperationException(); }
+}

Design Patterns/src/composite/SongGroup.java

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+package composite;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class SongGroup extends SongComponent {
+
+    private final List<SongComponent> songComponents = new ArrayList<>();
+    private final String groupName;
+    private final String groupDescription;
+
+    public SongGroup(String groupName, String groupDescription) {
+        this.groupName = groupName;
+        this.groupDescription = groupDescription;
+    }
+
+    public SongIterator createIterator() { return new SongIterator(songComponents); }
+
+    public String getGroupName() {
+        return groupName;
+    }
+
+    public String getGroupDescription() { return groupDescription; }
+
+    @Override
+    public void add(SongComponent songComponent) { songComponents.add(songComponent); }
+
+    @Override
+    public void remove(SongComponent songComponent) { songComponents.remove(songComponent); }
+
+    @Override
+    public SongComponent getComponent(int componentIndex) { return songComponents.get(componentIndex); }
+
+    @Override
+    public void displaySongInfo() {
+        System.out.println(getGroupName() + " " + getGroupDescription() + "\n");
+
+        SongIterator songIterator = createIterator();
+        while (songIterator.hasNext()) {
+            SongComponent songInfo = songIterator.next();
+            songInfo.displaySongInfo();
+        }
+    }
+}

Design Patterns/src/composite/SongIterator.java

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+package composite;
+
+import java.util.Iterator;
+import java.util.List;
+
+public class SongIterator implements Iterator<SongComponent> {
+    List<SongComponent> playList;
+    private int currentIndex = 0;
+
+    public SongIterator(List<SongComponent> playList) {
+        this.playList = playList;
+    }
+
+    @Override
+    public boolean hasNext() {
+        return currentIndex < playList.size();
+    }
+
+    @Override
+    public SongComponent next() {
+        if (this.hasNext()) {
+            return playList.get(currentIndex++);
+        }
+        return null;
+    }
+}