Added functionality to save playlists.

src/main/java/musicplayer/PlayerGUI.java

@@ -9,6 +9,7 @@ import musicplayer.model.Song;
 import musicplayer.swingmodels.PlaylistTableModel;
 
 import javax.swing.*;
+import javax.swing.filechooser.FileNameExtensionFilter;
 import javax.swing.tree.DefaultMutableTreeNode;
 import javax.swing.tree.DefaultTreeModel;
 import javax.swing.tree.TreeNode;
@@ -18,6 +19,7 @@ import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
 import java.awt.event.MouseListener;
 import java.io.File;
+import java.io.IOException;
 import java.nio.file.Path;
 import java.util.*;
 import java.util.List;
@@ -419,6 +421,38 @@ public class PlayerGUI implements PlayerCallbackInterface, LibraryCallbackInterf
 
         // Add everything to the menu bar itself
         menuBar.add(tools);
+
+        JMenu playlistTools = new JMenu("Playlist");
+        menuItem = new JMenuItem("Clear All");
+        menuItem.addActionListener((e) -> {
+            playlistTableModel.removeAll();
+            player.stop();
+        });
+        playlistTools.add(menuItem);
+
+        menuItem = new JMenuItem("Save Playlist");
+        menuItem.addActionListener(e -> {
+            if(!playlistTableModel.isEmpty()) {
+                JFileChooser fileChooser = new JFileChooser();
+                fileChooser.setDialogType(JFileChooser.SAVE_DIALOG);
+                fileChooser.setSelectedFile(new File("playlist.m3u"));
+                fileChooser.setFileFilter(new FileNameExtensionFilter("m3u playlist", "m3u"));
+                if (fileChooser.showSaveDialog(mainPanel) == JFileChooser.APPROVE_OPTION) {
+                    String filename = fileChooser.getSelectedFile().toString();
+                    if (!filename.endsWith(".m3u"))
+                        filename += ".m3u";
+                    try {
+                        playlistTableModel.writePlaylistToFile(new File(filename));
+                    } catch (IOException e1) {
+                        JOptionPane.showMessageDialog(null, e1.getMessage() + "\n" + Arrays.toString(e1.getStackTrace()), "Error", JOptionPane.ERROR_MESSAGE);
+                    }
+                }
+            }
+        });
+        playlistTools.add(menuItem);
+
+        // Add everything to the menu bar itself
+        menuBar.add(playlistTools);
         return menuBar;
     }
 

src/main/java/musicplayer/model/Song.java

@@ -132,4 +132,11 @@ public class Song implements Comparable<Song>, IDBType {
     public int compareTo(Song o) {
         return (trackNumber - o.getTrackNumber()) + ((discNumber - o.getDiscNumber()) * discNumberComparator);
     }
+
+    /**
+     * @return String that can be used to represent this song in an m3u format playlist file.
+     */
+    public String getM3UFormatString(){
+        return String.format("#EXTINF:0,%s - %s\n%s\n", getArtist().getName(), getTitle(), getSongFile().getAbsolutePath());
+    }
 }

src/main/java/musicplayer/swingmodels/PlaylistTableModel.java

@@ -3,6 +3,7 @@ package musicplayer.swingmodels;
 import musicplayer.model.Song;
 
 import javax.swing.table.AbstractTableModel;
+import java.io.*;
 import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
@@ -136,6 +137,13 @@ public class PlaylistTableModel extends AbstractTableModel {
         fireTableDataChanged();
     }
 
+    /**
+     * @return Is the playlist currently empty.
+     */
+    public boolean isEmpty(){
+        return songList.isEmpty();
+    }
+
     /**
      * Remove all songs from the playlist.
      */
@@ -161,4 +169,21 @@ public class PlaylistTableModel extends AbstractTableModel {
         playingRow = index;
         fireTableDataChanged();
     }
+
+    public String getM3UPlaylist(){
+        StringBuilder output = new StringBuilder("#EXTM3U\n");
+        songList.forEach(x -> output.append(x.getM3UFormatString()));
+        return output.toString();
+    }
+
+    public void writePlaylistToFile(File targetFile) throws IOException {
+        if(!targetFile.exists())
+            targetFile.createNewFile();
+        try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(targetFile), "utf-8"))) {
+            writer.write("#EXTM3U\n");
+            for(Song song : songList){
+               writer.write(song.getM3UFormatString());
+            }
+        }
+    }
 }