diff --git a/src/main/java/musicplayer/PlayerGUI.java b/src/main/java/musicplayer/PlayerGUI.java
index b8f74a1..6f61e1c 100644
--- a/src/main/java/musicplayer/PlayerGUI.java
+++ b/src/main/java/musicplayer/PlayerGUI.java
@@ -4,9 +4,7 @@ import com.google.inject.Guice;
 import com.google.inject.Inject;
 import com.google.inject.Injector;
 import musicplayer.callbacks.PlayerCallbackInterface;
-import musicplayer.db.IDatabase;
 import musicplayer.library.ILibrary;
-import musicplayer.model.Song;
 import musicplayer.player.IPlayer;
 import musicplayer.playlist.IPlaylist;
 import musicplayer.util.ConfigManager;
diff --git a/src/main/java/musicplayer/SwingUIModule.java b/src/main/java/musicplayer/SwingUIModule.java
index 9acc9bd..76e3f88 100644
--- a/src/main/java/musicplayer/SwingUIModule.java
+++ b/src/main/java/musicplayer/SwingUIModule.java
@@ -11,7 +11,7 @@ import musicplayer.player.IPlayer;
 import musicplayer.playlist.IPlaylist;
 import musicplayer.playlist.JTablePlaylist;
 
-public class SwingUIModule extends AbstractModule {
+class SwingUIModule extends AbstractModule {
 
     @Override
     protected void configure() {
diff --git a/src/main/java/musicplayer/callbacks/PlayerCallbackInterface.java b/src/main/java/musicplayer/callbacks/PlayerCallbackInterface.java
index a0ad802..c8a562f 100644
--- a/src/main/java/musicplayer/callbacks/PlayerCallbackInterface.java
+++ b/src/main/java/musicplayer/callbacks/PlayerCallbackInterface.java
@@ -2,7 +2,6 @@ package musicplayer.callbacks;
 
 import com.google.inject.ImplementedBy;
 import musicplayer.PlayerGUI;
-import musicplayer.model.Song;
 
 @ImplementedBy(PlayerGUI.class)
 public interface PlayerCallbackInterface {
diff --git a/src/main/java/musicplayer/db/HibernateDatabase.java b/src/main/java/musicplayer/db/HibernateDatabase.java
index d14b672..cbc6f3b 100644
--- a/src/main/java/musicplayer/db/HibernateDatabase.java
+++ b/src/main/java/musicplayer/db/HibernateDatabase.java
@@ -20,7 +20,7 @@ import java.util.Properties;
  */
 public class HibernateDatabase implements IDatabase{
 
-    private static SessionFactory sessionFactory;
+    private SessionFactory sessionFactory;
 
     /**
      * Create a database connection.
@@ -57,6 +57,8 @@ public class HibernateDatabase implements IDatabase{
                 .addAnnotatedClass(Artist.class)
                 .addAnnotatedClass(Song.class)
                 .buildSessionFactory();
+        Thread hookShutdown = new Thread(sessionFactory::close);
+        Runtime.getRuntime().addShutdownHook(hookShutdown);
     }
 
     /**
diff --git a/src/main/java/musicplayer/library/JTreeLibrary.java b/src/main/java/musicplayer/library/JTreeLibrary.java
index 5465ac6..34b653e 100644
--- a/src/main/java/musicplayer/library/JTreeLibrary.java
+++ b/src/main/java/musicplayer/library/JTreeLibrary.java
@@ -29,8 +29,8 @@ import java.util.stream.Collectors;
 
 public class JTreeLibrary extends JPanel implements ILibrary, LibraryCallbackInterface{
 
-    IDatabase database;
-    IPlaylist playlist;
+    private IDatabase database;
+    private IPlaylist playlist;
     private static final DefaultMutableTreeNode updatingNode = new DefaultMutableTreeNode();
     private final AtomicBoolean libraryUpdating = new AtomicBoolean(false);
     private final JComboBox<String> libraryDisplayType = new JComboBox<>();
@@ -182,7 +182,8 @@ public class JTreeLibrary extends JPanel implements ILibrary, LibraryCallbackInt
             int selRow = libraryTree.getRowForLocation(e.getX(), e.getY());
             if(e.getButton() == MouseEvent.BUTTON1 && e.getClickCount() == 2 && selRow != -1)
                 try {
-                    Object selectedItem = ((DefaultMutableTreeNode) libraryTree.getPathForLocation(e.getX(), e.getY()).getLastPathComponent()).getUserObject();
+                    @SuppressWarnings("ConstantConditions") Object selectedItem =
+                            ((DefaultMutableTreeNode) libraryTree.getPathForLocation(e.getX(), e.getY()).getLastPathComponent()).getUserObject();
                     if (selectedItem != null) {
                         if (selectedItem instanceof Song) {
                             playlist.addSong((Song) selectedItem);
@@ -198,6 +199,7 @@ public class JTreeLibrary extends JPanel implements ILibrary, LibraryCallbackInt
     private class LibraryTreeCellRenderer implements TreeCellRenderer {
 
         private final JLabel label;
+        @SuppressWarnings("ConstantConditions")
         private final Icon missingIcon = new ImageIcon(JTreeLibrary.class.getClassLoader().getResource("missing.gif"));
 
         LibraryTreeCellRenderer() {
diff --git a/src/main/java/musicplayer/model/Song.java b/src/main/java/musicplayer/model/Song.java
index 0610c4f..b621b26 100644
--- a/src/main/java/musicplayer/model/Song.java
+++ b/src/main/java/musicplayer/model/Song.java
@@ -1,16 +1,7 @@
 package musicplayer.model;
 
-import javax.imageio.ImageIO;
 import javax.persistence.*;
-import java.awt.image.BufferedImage;
 import java.io.File;
-import java.io.IOException;
-import java.nio.file.DirectoryStream;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.Paths;
-import java.util.NoSuchElementException;
-import java.util.Optional;
 
 @Entity
 public class Song implements Comparable<Song>, IDBType {