--- old/src/java.base/share/classes/java/io/File.java	2019-08-27 17:26:47.962324386 -0700
+++ new/src/java.base/share/classes/java/io/File.java	2019-08-27 17:26:47.786324386 -0700
@@ -2217,6 +2217,7 @@
      *
      * @serialData  Default fields followed by separator character.
      */
+    @java.io.Serial
     private synchronized void writeObject(java.io.ObjectOutputStream s)
         throws IOException
     {
@@ -2230,6 +2231,7 @@
      * than the separator character on this system, then the old separator
      * is replaced by the local separator.
      */
+    @java.io.Serial
     private synchronized void readObject(java.io.ObjectInputStream s)
          throws IOException, ClassNotFoundException
     {
@@ -2251,6 +2253,7 @@
             = UNSAFE.objectFieldOffset(File.class, "prefixLength");
 
     /** use serialVersionUID from JDK 1.0.2 for interoperability */
+    @java.io.Serial
     private static final long serialVersionUID = 301077366599181567L;
 
     // -- Integration with java.nio.file --