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

*** 1337,1346 ****
--- 1337,1347 ----
      /**
       * @serial include
       */
      abstract static class NavigableSubMap<K,V> extends AbstractMap<K,V>
          implements NavigableMap<K,V>, java.io.Serializable {
+         @java.io.Serial
          private static final long serialVersionUID = -2102997345730753016L;
          /**
           * The backing map.
           */
          final TreeMap<K,V> m;
*** 1842,1851 ****
--- 1843,1853 ----
  
      /**
       * @serial include
       */
      static final class AscendingSubMap<K,V> extends NavigableSubMap<K,V> {
+         @java.io.Serial
          private static final long serialVersionUID = 912986545866124060L;
  
          AscendingSubMap(TreeMap<K,V> m,
                          boolean fromStart, K lo, boolean loInclusive,
                          boolean toEnd,     K hi, boolean hiInclusive) {
*** 1925,1934 ****
--- 1927,1937 ----
  
      /**
       * @serial include
       */
      static final class DescendingSubMap<K,V>  extends NavigableSubMap<K,V> {
+         @java.io.Serial
          private static final long serialVersionUID = 912986545866120460L;
          DescendingSubMap(TreeMap<K,V> m,
                          boolean fromStart, K lo, boolean loInclusive,
                          boolean toEnd,     K hi, boolean hiInclusive) {
              super(m, fromStart, lo, loInclusive, toEnd, hi, hiInclusive);
*** 2017,2029 ****
--- 2020,2034 ----
       *
       * @serial include
       */
      private class SubMap extends AbstractMap<K,V>
          implements SortedMap<K,V>, java.io.Serializable {
+         @java.io.Serial
          private static final long serialVersionUID = -6520786458950516097L;
          private boolean fromStart = false, toEnd = false;
          private K fromKey, toKey;
+         @java.io.Serial
          private Object readResolve() {
              return new AscendingSubMap<>(TreeMap.this,
                                           fromStart, fromKey, true,
                                           toEnd, toKey, false);
          }
*** 2404,2413 ****
--- 2409,2419 ----
          }
  
          setColor(x, BLACK);
      }
  
+    @java.io.Serial
     private static final long serialVersionUID = 919286545866124006L;
  
      /**
       * Save the state of the {@code TreeMap} instance to a stream (i.e.,
       * serialize it).
*** 2418,2427 ****
--- 2424,2434 ----
       *             by the TreeMap. The key-value mappings are emitted in
       *             key-order (as determined by the TreeMap's Comparator,
       *             or by the keys' natural ordering if the TreeMap has no
       *             Comparator).
       */
+     @java.io.Serial
      private void writeObject(java.io.ObjectOutputStream s)
          throws java.io.IOException {
          // Write out the Comparator and any hidden stuff
          s.defaultWriteObject();
  
*** 2437,2446 ****
--- 2444,2454 ----
  
      /**
       * Reconstitute the {@code TreeMap} instance from a stream (i.e.,
       * deserialize it).
       */
+     @java.io.Serial
      private void readObject(final java.io.ObjectInputStream s)
          throws java.io.IOException, ClassNotFoundException {
          // Read in the Comparator and any hidden stuff
          s.defaultReadObject();