src/java.base/share/classes/java/lang/Throwable.java

*** 112,121 ****
--- 112,122 ----
   * @jls 11.2 Compile-Time Checking of Exceptions
   * @since 1.0
   */
  public class Throwable implements Serializable {
      /** use serialVersionUID from JDK 1.0.2 for interoperability */
+     @java.io.Serial
      private static final long serialVersionUID = -3042686055658047285L;
  
      /**
       * The JVM saves some indication of the stack backtrace in this slot.
       */
*** 899,908 ****
--- 900,910 ----
       *
       * Note that there are no constraints on the value the {@code
       * cause} field can hold; both {@code null} and {@code this} are
       * valid values for the field.
       */
+     @java.io.Serial
      private void readObject(ObjectInputStream s)
          throws IOException, ClassNotFoundException {
          s.defaultReadObject();     // read in all fields
  
          // Set suppressed exceptions and stack trace elements fields
*** 987,996 ****
--- 989,999 ----
       *
       * A {@code null} stack trace field is represented in the serial
       * form as a one-element array whose element is equal to {@code
       * new StackTraceElement("", "", null, Integer.MIN_VALUE)}.
       */
+     @java.io.Serial
      private synchronized void writeObject(ObjectOutputStream s)
          throws IOException {
          // Ensure that the stackTrace field is initialized to a
          // non-null value, if appropriate.  As of JDK 7, a null stack
          // trace field is a valid value indicating the stack trace