8254161: Prevent instantiation of EnumSet subclasses through deserialization

Reviewed-by: dfuchs, alanb, rriggs, smarks

src/java.base/share/classes/java/util/EnumSet.java

@@ -480,6 +480,7 @@ public abstract class EnumSet<E extends Enum<E>> extends AbstractSet<E>
     }
 
     /**
+     * Throws {@code InvalidObjectException}.
      * @param s the stream
      * @throws java.io.InvalidObjectException always
      */
@@ -488,4 +489,14 @@ public abstract class EnumSet<E extends Enum<E>> extends AbstractSet<E>
         throws java.io.InvalidObjectException {
         throw new java.io.InvalidObjectException("Proxy required");
     }
+
+    /**
+     * Throws {@code InvalidObjectException}.
+     * @throws java.io.InvalidObjectException always
+     */
+    @java.io.Serial
+    private void readObjectNoData()
+        throws java.io.InvalidObjectException {
+        throw new java.io.InvalidObjectException("Proxy required");
+    }
 }