--- old/src/java.base/share/classes/java/util/Hashtable.java	2019-08-27 17:28:58.418324386 -0700
+++ new/src/java.base/share/classes/java/util/Hashtable.java	2019-08-27 17:28:58.250324386 -0700
@@ -171,6 +171,7 @@
     private transient int modCount = 0;
 
     /** use serialVersionUID from JDK 1.0.2 for interoperability */
+    @java.io.Serial
     private static final long serialVersionUID = 1421746759512286392L;
 
     /**
@@ -1201,6 +1202,7 @@
      *             for each key-value mapping represented by the Hashtable
      *             The key-value mappings are emitted in no particular order.
      */
+    @java.io.Serial
     private void writeObject(java.io.ObjectOutputStream s)
             throws IOException {
         writeHashtable(s);
@@ -1254,6 +1256,7 @@
     /**
      * Reconstitute the Hashtable from a stream (i.e., deserialize it).
      */
+    @java.io.Serial
     private void readObject(java.io.ObjectInputStream s)
             throws IOException, ClassNotFoundException {
         readHashtable(s);