--- old/src/java.base/share/classes/java/util/IdentityHashMap.java	2019-08-27 17:28:58.918324386 -0700
+++ new/src/java.base/share/classes/java/util/IdentityHashMap.java	2019-08-27 17:28:58.722324386 -0700
@@ -1259,7 +1259,7 @@
         }
     }
 
-
+    @java.io.Serial
     private static final long serialVersionUID = 8188218128353913216L;
 
     /**
@@ -1272,6 +1272,7 @@
      *          IdentityHashMap.  The key-value mappings are emitted in no
      *          particular order.
      */
+    @java.io.Serial
     private void writeObject(java.io.ObjectOutputStream s)
         throws java.io.IOException  {
         // Write out and any hidden stuff
@@ -1295,6 +1296,7 @@
      * Reconstitutes the {@code IdentityHashMap} instance from a stream (i.e.,
      * deserializes it).
      */
+    @java.io.Serial
     private void readObject(java.io.ObjectInputStream s)
         throws java.io.IOException, ClassNotFoundException  {
         // Read in any hidden stuff