diff --git a/fine-poi-old/src/main/java/com/fr/third/org/apache/poi/hssf/record/WindowTwoRecord.java b/fine-poi-old/src/main/java/com/fr/third/org/apache/poi/hssf/record/WindowTwoRecord.java
index d6a93e988..6ca0e33bd 100644
--- a/fine-poi-old/src/main/java/com/fr/third/org/apache/poi/hssf/record/WindowTwoRecord.java
+++ b/fine-poi-old/src/main/java/com/fr/third/org/apache/poi/hssf/record/WindowTwoRecord.java
@@ -39,23 +39,21 @@ public class WindowTwoRecord
     private short             field_1_options;
 
     // bitfields
-    private BitField          displayFormulas         = BitFieldFactory.getInstance(0x01);
-    private BitField          displayGridlines        = BitFieldFactory.getInstance(0x02);
-    private BitField          displayRowColHeadings   = BitFieldFactory.getInstance(0x04);
-    private BitField          freezePanes             = BitFieldFactory.getInstance(0x08);
-    private BitField          displayZeros            = BitFieldFactory.getInstance(0x10);
-    private BitField          defaultHeader           =
-        BitFieldFactory.getInstance(0x20);   // if false use color in field 4
+    private static final BitField displayFormulas = BitFieldFactory.getInstance(0x01);
+    private static final BitField displayGridlines = BitFieldFactory.getInstance(0x02);
+    private static final BitField displayRowColHeadings = BitFieldFactory.getInstance(0x04);
+    private static final BitField freezePanes = BitFieldFactory.getInstance(0x08);
+    private static final BitField displayZeros = BitFieldFactory.getInstance(0x10);
+    private static final BitField defaultHeader = BitFieldFactory.getInstance(0x20);   // if false use color in field 4
 
     // if true use default foreground
     // for headers
-    private BitField          arabic                  =
-        BitFieldFactory.getInstance(0x40);   // for our desert dwelling friends
-    private BitField          displayGuts             = BitFieldFactory.getInstance(0x80);
-    private BitField          freezePanesNoSplit      = BitFieldFactory.getInstance(0x100);
-    private BitField          selected                = BitFieldFactory.getInstance(0x200);
-    private BitField          active                  = BitFieldFactory.getInstance(0x400);
-    private BitField          savedInPageBreakPreview = BitFieldFactory.getInstance(0x800);
+    private static final BitField arabic = BitFieldFactory.getInstance(0x40);   // for our desert dwelling friends
+    private static final BitField displayGuts = BitFieldFactory.getInstance(0x80);
+    private static final BitField freezePanesNoSplit = BitFieldFactory.getInstance(0x100);
+    private static final BitField selected = BitFieldFactory.getInstance(0x200);
+    private static final BitField active = BitFieldFactory.getInstance(0x400);
+    private static final BitField savedInPageBreakPreview = BitFieldFactory.getInstance(0x800);
 
     // 4-7 reserved
     // end bitfields
diff --git a/fine-poi-old/src/main/java/com/fr/third/org/apache/poi/util/BitFieldFactory.java b/fine-poi-old/src/main/java/com/fr/third/org/apache/poi/util/BitFieldFactory.java
index ad40eee30..3f4e493ce 100644
--- a/fine-poi-old/src/main/java/com/fr/third/org/apache/poi/util/BitFieldFactory.java
+++ b/fine-poi-old/src/main/java/com/fr/third/org/apache/poi/util/BitFieldFactory.java
@@ -19,7 +19,7 @@
 
 package com.fr.third.org.apache.poi.util;
 
-import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
 
 /**
  * Returns immutable Btfield instances.
@@ -27,18 +27,11 @@ import java.util.*;
  * @author Jason Height (jheight at apache dot org)
  */
 
-public class BitFieldFactory
-{
-    private static Map instances = new HashMap();
-    
-    public static BitField getInstance(final int mask) {
-      BitField f = (BitField)instances.get(new Integer(mask));
-      if (f == null) {
-        f = new BitField(mask);
-        instances.put(new Integer(mask), f);        
-      }
-      return f;
-    }
+public class BitFieldFactory {
+    private static final ConcurrentHashMap<Integer, BitField> instances = new ConcurrentHashMap<>();
 
+    public static BitField getInstance(int mask) {
+        return instances.computeIfAbsent(mask, k -> new BitField(mask));
+    }
 }   // end public class BitFieldFactory