src/java.base/share/classes/java/time/Ser.java

@@ -89,10 +89,11 @@
 final class Ser implements Externalizable {
 
     /**
      * Serialization version.
      */
+    @java.io.Serial
     private static final long serialVersionUID = -7683839454370182990L;
 
     static final byte DURATION_TYPE = 1;
     static final byte INSTANT_TYPE = 2;
     static final byte LOCAL_DATE_TYPE = 3;

@@ -275,10 +276,11 @@
     /**
      * Returns the object that will replace this one.
      *
      * @return the read object, should never be null
      */
+    @java.io.Serial
     private Object readResolve() {
          return object;
     }
 
 }