diff --git a/app/src/main/java/com/mkulesh/mmd/AtomPainter.java b/app/src/main/java/com/mkulesh/mmd/AtomPainter.java
index 35af3c7..8473309 100644
--- a/app/src/main/java/com/mkulesh/mmd/AtomPainter.java
+++ b/app/src/main/java/com/mkulesh/mmd/AtomPainter.java
@@ -80,14 +80,14 @@ enum BackgroudMode
     private ZoomPanel zoomPanel = null;
     private Context context = null;
     private SurfaceHolder holder = null;
-    private WallpaperOffsets wallpaperOffsets = new WallpaperOffsets();
+    private final WallpaperOffsets wallpaperOffsets = new WallpaperOffsets();
 
     // synchronization with calculation thread
     private BlockingQueue<AtomSet> waitingQueue = null, immediateQueue = null;
 
     // thread implementation
     private Thread thread = null;
-    private ThreadContol threadControl = new ThreadContol();
+    private final ThreadContol threadControl = new ThreadContol();
 
     // timing statistic and fps control
     private static final float maxFps = 25.0f;
diff --git a/app/src/main/java/com/mkulesh/mmd/Experiment.java b/app/src/main/java/com/mkulesh/mmd/Experiment.java
index 2a95e0d..3ec7af1 100644
--- a/app/src/main/java/com/mkulesh/mmd/Experiment.java
+++ b/app/src/main/java/com/mkulesh/mmd/Experiment.java
@@ -97,7 +97,7 @@ public static class Options
      * Private attributes to be created internally
      */
     private Context context = null;
-    private ThreadContol threadControl = new ThreadContol();
+    private final ThreadContol threadControl = new ThreadContol();
     private AtomPainter painter = null;
     private Thread thread = null;