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

*** 81,90 ****
--- 81,91 ----
       *
       * The bits in this BitSet.  The ith bit is stored in bits[i/64] at
       * bit position i % 64 (where bit position 0 refers to the least
       * significant bit and 63 refers to the most significant bit).
       */
+     @java.io.Serial
      private static final ObjectStreamField[] serialPersistentFields = {
          new ObjectStreamField("bits", long[].class),
      };
  
      /**
*** 102,111 ****
--- 103,113 ----
       * the user knows what he's doing and try harder to preserve it.
       */
      private transient boolean sizeIsSticky = false;
  
      /* use serialVersionUID from JDK 1.0.2 for interoperability */
+     @java.io.Serial
      private static final long serialVersionUID = 7997698588986878753L;
  
      /**
       * Given a bit index, return word index containing it.
       */
*** 1122,1131 ****
--- 1124,1134 ----
  
      /**
       * Save the state of the {@code BitSet} instance to a stream (i.e.,
       * serialize it).
       */
+     @java.io.Serial
      private void writeObject(ObjectOutputStream s)
          throws IOException {
  
          checkInvariants();
  
*** 1139,1148 ****
--- 1142,1152 ----
  
      /**
       * Reconstitute the {@code BitSet} instance from a stream (i.e.,
       * deserialize it).
       */
+     @java.io.Serial
      private void readObject(ObjectInputStream s)
          throws IOException, ClassNotFoundException {
  
          ObjectInputStream.GetField fields = s.readFields();
          words = (long[]) fields.get("bits", null);