diff a/src/java.base/share/classes/java/lang/StringBuffer.java b/src/java.base/share/classes/java/lang/StringBuffer.java
--- a/src/java.base/share/classes/java/lang/StringBuffer.java
+++ b/src/java.base/share/classes/java/lang/StringBuffer.java
@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 1994, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
@@ -23,10 +23,11 @@
  * questions.
  */
 
 package java.lang;
 
+import java.io.IOException;
 import java.util.Arrays;
 import jdk.internal.HotSpotIntrinsicCandidate;
 
 /**
  * A thread-safe, mutable sequence of characters.
@@ -731,12 +732,15 @@
         new java.io.ObjectStreamField("count", Integer.TYPE),
         new java.io.ObjectStreamField("shared", Boolean.TYPE),
     };
 
     /**
-     * readObject is called to restore the state of the StringBuffer from
+     * The {@code writeObject} method is called to write the state of the {@code StringBuffer} to
      * a stream.
+     *
+     * @param  s the {@code ObjectOutputStream} to which data is written
+     * @throws IOException if an I/O error occurs
      */
     @java.io.Serial
     private synchronized void writeObject(java.io.ObjectOutputStream s)
         throws java.io.IOException {
         java.io.ObjectOutputStream.PutField fields = s.putFields();
@@ -751,12 +755,16 @@
         fields.put("shared", false);
         s.writeFields();
     }
 
     /**
-     * readObject is called to restore the state of the StringBuffer from
+     * The {@code readObject} method is called to restore the state of the {@code StringBuffer} from
      * a stream.
+     *
+     * @param  s the {@code ObjectInputStream} from which data is read
+     * @throws IOException if an I/O error occurs
+     * @throws ClassNotFoundException if a serialized class cannot be loaded
      */
     @java.io.Serial
     private void readObject(java.io.ObjectInputStream s)
         throws java.io.IOException, ClassNotFoundException {
         java.io.ObjectInputStream.GetField fields = s.readFields();
