diff --git a/build.gradle b/build.gradle
index 4f04824..489141e 100644
--- a/build.gradle
+++ b/build.gradle
@@ -7,7 +7,7 @@ apply plugin: 'jacoco'
 apply plugin: 'application'
 
 
-mainClassName = "PanoViewer.PanoViewer"
+mainClassName = "org.panoviewer.PanoViewer"
 
 configurations {
   // configuration that holds jars to include in the jar
diff --git a/src/main/java/org/panoviewer/PanoViewer.java b/src/main/java/org/panoviewer/PanoViewer.java
index 03b3452..310dc7f 100644
--- a/src/main/java/org/panoviewer/PanoViewer.java
+++ b/src/main/java/org/panoviewer/PanoViewer.java
@@ -1,6 +1,8 @@
 // License: GPL. For details, see LICENSE file.
 package org.panoviewer;
 
+import org.panoviewer.gui.MainScreen;
+
 /**
  *
  * @author kshan
diff --git a/src/main/java/org/panoviewer/MainScreen.java b/src/main/java/org/panoviewer/gui/MainScreen.java
similarity index 82%
rename from src/main/java/org/panoviewer/MainScreen.java
rename to src/main/java/org/panoviewer/gui/MainScreen.java
index 69281eb..3bf81ac 100644
--- a/src/main/java/org/panoviewer/MainScreen.java
+++ b/src/main/java/org/panoviewer/gui/MainScreen.java
@@ -1,29 +1,34 @@
 // License: GPL. For details, see LICENSE file.
-package org.panoviewer;
+package org.panoviewer.gui;
 
 import org.panoviewer.utils.IOUtils;
-import org.panoviewer.gui.Menu;
 import javax.swing.*;
 import java.awt.datatransfer.DataFlavor;
 import java.awt.datatransfer.Transferable;
+import java.awt.datatransfer.UnsupportedFlavorException;
 import java.awt.dnd.*;
 import java.awt.image.BufferedImage;
 import java.io.File;
 import java.util.List;
 
 import static java.awt.dnd.DnDConstants.ACTION_COPY;
+import java.io.IOException;
 
 public class MainScreen extends JFrame implements DropTargetListener {
 
-  private JMenuBar menuBar = Menu.getInstance();
-  private JPanel jPanel;
-  private static MainScreen instance = new MainScreen();
+  private final JMenuBar menuBar;
+  private final JPanel jPanel;
+  private static MainScreen instance;
 
   public static MainScreen getInstance() {
+    if (instance == null) {
+      instance = new MainScreen();
+    }
     return instance;
   }
 
   private MainScreen() {
+    this.menuBar = Menu.getInstance();
     setSize(600, 600);
     setVisible(true);
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
@@ -70,8 +75,7 @@ public void drop(DropTargetDropEvent event) {
           List<File> files = (List<File>) transferable.getTransferData(df);
           displayImage(files.get(0));
         }
-      } catch (Exception e) {
-        e.printStackTrace();
+      } catch (UnsupportedFlavorException | IOException e) {
       }
     }
   }
diff --git a/src/main/java/org/panoviewer/gui/Menu.java b/src/main/java/org/panoviewer/gui/Menu.java
index 125964e..a745ce2 100644
--- a/src/main/java/org/panoviewer/gui/Menu.java
+++ b/src/main/java/org/panoviewer/gui/Menu.java
@@ -1,7 +1,6 @@
 // License: GPL. For details, see LICENSE file.
 package org.panoviewer.gui;
 
-import org.panoviewer.MainScreen;
 import org.panoviewer.Mode;
 import org.panoviewer.ModeRecorder;
 import org.panoviewer.utils.IOUtils;
diff --git a/src/main/java/org/panoviewer/SwitchModes.java b/src/main/java/org/panoviewer/gui/SwitchModes.java
similarity index 95%
rename from src/main/java/org/panoviewer/SwitchModes.java
rename to src/main/java/org/panoviewer/gui/SwitchModes.java
index aa5cc4a..f749b50 100644
--- a/src/main/java/org/panoviewer/SwitchModes.java
+++ b/src/main/java/org/panoviewer/gui/SwitchModes.java
@@ -1,5 +1,5 @@
 // License: GPL. For details, see LICENSE file.
-package org.panoviewer;
+package org.panoviewer.gui;
 
 import org.panoviewer.gui.jogl.FlatPanel;
 import org.panoviewer.gui.jogl.PanoramicPanel;
@@ -8,6 +8,8 @@
 import java.awt.image.BufferedImage;
 import java.beans.PropertyChangeEvent;
 import java.beans.PropertyChangeListener;
+import org.panoviewer.Mode;
+import org.panoviewer.ModeRecorder;
 
 import static org.panoviewer.utils.imageutils.isRatio;
 
diff --git a/src/main/java/org/panoviewer/utils/IOUtils.java b/src/main/java/org/panoviewer/utils/IOUtils.java
index 50a0db0..7ba8a9c 100644
--- a/src/main/java/org/panoviewer/utils/IOUtils.java
+++ b/src/main/java/org/panoviewer/utils/IOUtils.java
@@ -11,8 +11,8 @@
 
 import java.awt.image.BufferedImage;
 import org.panoviewer.FileChooser;
-import org.panoviewer.MainScreen;
-import org.panoviewer.SwitchModes;
+import org.panoviewer.gui.MainScreen;
+import org.panoviewer.gui.SwitchModes;
 
 /**
  *
diff --git a/src/test/java/org/panoviewer/CameraTest.java b/src/test/java/org/panoviewer/CameraTest.java
index e5ba4ef..7832929 100644
--- a/src/test/java/org/panoviewer/CameraTest.java
+++ b/src/test/java/org/panoviewer/CameraTest.java
@@ -1,13 +1,14 @@
 // License: GPL. For details, see LICENSE file.
 package org.panoviewer;
 
-import junit.framework.TestCase;
+import static junit.framework.TestCase.assertEquals;
+import static junit.framework.TestCase.assertTrue;
 import org.junit.Test;
 
 /**
  * Tests {@link Camera}
  */
-public class CameraTest extends TestCase {
+public class CameraTest {
 
   public CameraTest() {
   }