Player now properly handles empty playlists and songs with missing files.

src/main/java/musicplayer/Player.java

@@ -8,6 +8,7 @@ import org.gstreamer.State;
 import org.gstreamer.elements.PlayBin2;
 
 import java.io.File;
+import java.util.Optional;
 
 public class Player {
 
@@ -43,25 +44,32 @@ public class Player {
 
     /**
      * Set a source Song file and start playing it via GStreamer.
-     * @param song Song to play.
+     * @param inputSong Song to play.
      */
-    public void playSong(Song song) {
+    public void playSong(Optional<Song> inputSong){
-        callbackInterface.setSongHighlighting(song);
-        currentSong = song;
-        File songFile = song.getSongFile();
         if (playBin.getState() == State.PLAYING)
             stop();
         playBin.setState(State.READY);
+        if(inputSong.isPresent()) {
+            currentSong = inputSong.get();
+            callbackInterface.setSongHighlighting(currentSong);
+            File songFile = currentSong.getSongFile();
+            if (!songFile.exists()) {
+                callbackInterface.removeInvalidSong(currentSong);
+                playSong(callbackInterface.getNextSong(currentSong));
+                return;
+            }
             playBin.setURI(songFile.toURI());
             internalThread = new InternalThread();
             thread = new Thread(internalThread);
             playBin.play();
             thread.start();
-        while(true){
+            while (true) {
                 if (playBin.isPlaying()) break;
             } // Wait for song to actually be playing otherwise queryDuration is always zero
             callbackInterface.setSeekBarDuration((int) playBin.queryDuration().toSeconds());
         }
+    }
 
     /**
      * Stop any music currently playing.

src/main/java/musicplayer/PlayerGUI.java

@@ -66,7 +66,7 @@ public class PlayerGUI implements PlayerCallbackInterface, LibraryCallbackInterf
         //Action Listeners
         playButton.addActionListener(e -> {
             if (playList.getRowCount() > 0) {
-                player.playSong(playlistTableModel.getFirst().get());
+                player.playSong(playlistTableModel.getFirst());
             }
         });
         MouseListener mouseListener = new libraryMouseAdapter();
@@ -150,7 +150,7 @@ public class PlayerGUI implements PlayerCallbackInterface, LibraryCallbackInterf
      * @return The next song to be selected.
      */
     @Override
-    public Song getNextSong(Song currentSong) {
+    public Optional<Song> getNextSong(Song currentSong) {
         return playlistTableModel.nextSong(currentSong);
     }
 
@@ -180,6 +180,11 @@ public class PlayerGUI implements PlayerCallbackInterface, LibraryCallbackInterf
         SwingUtilities.invokeLater(() -> seekBar.setMaximum(seconds));
     }
 
+    @Override
+    public void removeInvalidSong(Song invalidSong) {
+        playlistTableModel.removeSong(invalidSong);
+    }
+
     public void refreshLibrary(){
         DefaultTreeModel model = new DefaultTreeModel(new DefaultMutableTreeNode());
         DefaultMutableTreeNode parentNode = (DefaultMutableTreeNode) model.getRoot();
@@ -261,4 +266,5 @@ public class PlayerGUI implements PlayerCallbackInterface, LibraryCallbackInterf
     private void setVolumeValue(int value){
         volumeValue.setText(String.format("%d%%", value));
     }
+
 }

src/main/java/musicplayer/PlaylistTableModel.java

@@ -66,10 +66,10 @@ public class PlaylistTableModel extends AbstractTableModel {
         return songList.size() > 0 ? Optional.of(songList.get(0)) : Optional.<Song>empty();
     }
 
-    public Song nextSong(Song song){
+    public Optional<Song> nextSong(Song song){
         int index = songList.indexOf(song) + 1;
         if(index >= songList.size()) index = 0;
-        return songList.get(index);
+        return songList.size() > 0 ? Optional.of(songList.get(index)) : Optional.empty();
     }
 
     public Song previous(Song song){
@@ -94,4 +94,9 @@ public class PlaylistTableModel extends AbstractTableModel {
         Collections.reverse(indices);
         indices.forEach(this::removeSong);
     }
+
+    public void removeSong(Song song){
+        songList.remove(song);
+        fireTableDataChanged();
+    }
 }

src/main/java/musicplayer/callbacks/PlayerCallbackInterface.java

@@ -2,12 +2,16 @@ package musicplayer.callbacks;
 
 import musicplayer.model.Song;
 
+import java.util.Optional;
+
 public interface PlayerCallbackInterface {
 
-    Song getNextSong(Song currentSong);
+    Optional<Song> getNextSong(Song currentSong);
 
     void setSongHighlighting(Song playingSong);
 
     void setSeekBarDuration(int seconds);
 
+    void removeInvalidSong(Song invalidSong);
+
 }