src/java.base/share/classes/java/net/URL.java

*** 173,182 ****
--- 173,183 ----
   * @since 1.0
   */
  public final class URL implements java.io.Serializable {
  
      static final String BUILTIN_HANDLERS_PREFIX = "sun.net.www.protocol";
+     @java.io.Serial
      static final long serialVersionUID = -7627629688361524110L;
  
      /**
       * The property which specifies the package prefix list to be scanned
       * for protocol handlers.  The value of this property (if any) should
*** 1487,1496 ****
--- 1488,1498 ----
       * @serialField    ref String
       *
       * @serialField    hashCode int
       *
       */
+     @java.io.Serial
      private static final ObjectStreamField[] serialPersistentFields = {
          new ObjectStreamField("protocol", String.class),
          new ObjectStreamField("host", String.class),
          new ObjectStreamField("port", int.class),
          new ObjectStreamField("authority", String.class),
*** 1506,1515 ****
--- 1508,1518 ----
       * @serialData the default write object value. When read back in,
       * the reader must ensure that calling getURLStreamHandler with
       * the protocol variable returns a valid URLStreamHandler and
       * throw an IOException if it does not.
       */
+     @java.io.Serial
      private synchronized void writeObject(java.io.ObjectOutputStream s)
          throws IOException
      {
          s.defaultWriteObject(); // write the fields
      }
*** 1517,1526 ****
--- 1520,1530 ----
      /**
       * readObject is called to restore the state of the URL from the
       * stream.  It reads the components of the URL and finds the local
       * stream handler.
       */
+     @java.io.Serial
      private synchronized void readObject(java.io.ObjectInputStream s)
              throws IOException, ClassNotFoundException {
          GetField gf = s.readFields();
          String protocol = (String)gf.get("protocol", null);
          if (getURLStreamHandler(protocol) == null) {
*** 1548,1558 ****
       * @return a newly created object from deserialized data
       *
       * @throws ObjectStreamException if a new object replacing this
       * object could not be created
       */
! 
     private Object readResolve() throws ObjectStreamException {
  
          URLStreamHandler handler = null;
          // already been checked in readObject
          handler = getURLStreamHandler(tempState.getProtocol());
--- 1552,1562 ----
       * @return a newly created object from deserialized data
       *
       * @throws ObjectStreamException if a new object replacing this
       * object could not be created
       */
!    @java.io.Serial
     private Object readResolve() throws ObjectStreamException {
  
          URLStreamHandler handler = null;
          // already been checked in readObject
          handler = getURLStreamHandler(tempState.getProtocol());