commit 07d9e55f207eddca9b7ebf551b679915f03e70f4
Author: Leszek Koltunski <leszek@koltunski.pl>
Date:   Sun Dec 5 22:19:21 2021 +0100

    Progress replacing the enum ObjetType with the class RubikObjectList.

diff --git a/src/main/java/org/distorted/library/main/InternalStackFrame.java b/src/main/java/org/distorted/library/main/InternalStackFrame.java
index c7d2be6..f69a8fb 100644
--- a/src/main/java/org/distorted/library/main/InternalStackFrame.java
+++ b/src/main/java/org/distorted/library/main/InternalStackFrame.java
@@ -51,23 +51,23 @@ public class InternalStackFrame
       }
     }
 
-  private static LinkedList<InternalObject> mCommonDoneList = new LinkedList<>(); //
-  private static HashMap<Long,Job> mCommonToDoMap           = new HashMap<>();    // Common
-  private static long mCommonNextClientID                   = 0;                  // InternalObject
-  private static long mCommonNextSystemID                   = 0;                  // (postprocessing)
+  private static final LinkedList<InternalObject> mCommonDoneList = new LinkedList<>(); //
+  private static final HashMap<Long,Job> mCommonToDoMap           = new HashMap<>();    // Common
+  private static long mCommonNextClientID                         = 0;                  // InternalObject
+  private static long mCommonNextSystemID                         = 0;                  // (postprocessing)
 
   //////////////////////////////////////////////////////////////////
-  private LinkedList<InternalObject> mDoneList;                   //
-  private HashMap<Long,Job> mToDoMap;                             //
+  private final LinkedList<InternalObject> mDoneList;             //
+  private final HashMap<Long,Job> mToDoMap;                       //
+  private final long mTaskId;                                     //
   private long mNextClientID;                                     // InternalObject
   private long mNextSystemID;                                     //
-  private long mTaskId;                                           //
 
   //////////////////////////////////////////////////////////////////
   private boolean mInitialized;                                   // DistortedLibrary
 
   //////////////////////////////////////////////////////////////////
-  private int[] mMax;                                             // EffectQueue
+  private final int[] mMax;                                       // EffectQueue
 
   //////////////////////////////////////////////////////////////////
   private long mNextEffectsID;                                    // DistortedEffects;
@@ -80,11 +80,11 @@ public class InternalStackFrame
   private long mNextNodeID;
 
   //////////////////////////////////////////////////////////////////
-  private ArrayList<InternalMaster.Slave> mSlaves;                // InternalMaster
+  private final ArrayList<InternalMaster.Slave> mSlaves;          // InternalMaster
 
   ////////////////////////////////////////////////////////////////// EffectQueue
   private long mNextQueueID;                                      //
-  private HashMap<ArrayList<Long>,Long> mMapID;                   // maps lists of Effect IDs (longs)
+  private final HashMap<ArrayList<Long>,Long> mMapID;             // maps lists of Effect IDs (longs)
                                                                   // to a single long - the queue ID.
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////