src/java.base/share/classes/java/math/BigDecimal.java

@@ -278,10 +278,11 @@
     // All 18-digit base ten strings fit into a long; not all 19-digit
     // strings will
     private static final int MAX_COMPACT_DIGITS = 18;
 
     /* Appease the serialization gods */
+    @java.io.Serial
     private static final long serialVersionUID = 6108874887143696463L;
 
     private static final ThreadLocal<StringBuilderHelper>
         threadLocalStringBuilderHelper = new ThreadLocal<StringBuilderHelper>() {
         @Override

@@ -4125,10 +4126,11 @@
      * Reconstitute the {@code BigDecimal} instance from a stream (that is,
      * deserialize it).
      *
      * @param s the stream being read.
      */
+    @java.io.Serial
     private void readObject(java.io.ObjectInputStream s)
         throws java.io.IOException, ClassNotFoundException {
         // Read in all fields
         s.defaultReadObject();
         // validate possibly bad fields

@@ -4143,10 +4145,11 @@
    /**
     * Serialize this {@code BigDecimal} to the stream in question
     *
     * @param s the stream to serialize to.
     */
+    @java.io.Serial
    private void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException {
        // Must inflate to maintain compatible serial form.
        if (this.intVal == null)
            UnsafeHolder.setIntValVolatile(this, BigInteger.valueOf(this.intCompact));