implement music player + JavaFx UI

src/main/java/sbu/javafx/PlaylistController.java

@@ -0,0 +1,57 @@
+package sbu.javafx;
+
+import javafx.fxml.FXML;
+import javafx.scene.control.ListView;
+import javafx.scene.control.Alert;
+import javafx.scene.control.ButtonType;
+import javafx.stage.Stage;
+import javafx.scene.Scene;
+import javafx.fxml.FXMLLoader;
+import java.io.IOException;
+import java.util.ArrayList;
+
+public class PlaylistController
+{
+
+    @FXML
+    private ListView<String> playlistListView;
+
+    private ArrayList<Song> playlist = new ArrayList<>();
+
+    public void setPlaylist(ArrayList<Song> playlist)
+    {
+        this.playlist = playlist;
+        refreshPlaylist();
+    }
+
+    private void refreshPlaylist()
+    {
+        playlistListView.getItems().clear();
+
+        if (playlist.isEmpty())
+            playlistListView.getItems().add("Playlist is empty.");
+        else
+            for (Song song : playlist)
+                playlistListView.getItems().add(song.toString());
+    }
+
+    @FXML
+    private void goBack()
+    {
+        try
+        {
+            FXMLLoader loader = new FXMLLoader(MusicApp.class.getResource("App-view.fxml"));
+            Scene scene = new Scene(loader.load(), 1280, 900);
+
+            Stage stage = (Stage) playlistListView.getScene().getWindow();
+            stage.setScene(scene);
+            stage.setTitle("Music Player");
+        }
+        catch (IOException e)
+        {
+            e.printStackTrace();
+            Alert alert = new Alert(Alert.AlertType.ERROR, "Failed to return to main screen.", ButtonType.OK);
+            alert.showAndWait();
+        }
+    }
+}