code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.Hashtable;
  
  /*
   * Copyright 2003 Sun Microsystems, Inc.  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.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
   * CA 95054 USA or visit www.sun.com if you need additional information or
   * have any questions.
   */
  
  /**
   * @test
   * @bug 4652911
   * @summary test Hashtable readObject for invocation of overridable put method
   */
  import java.util.Hashtable;
  
  import java.io.ByteArrayOutputStream;
  import java.io.ObjectOutputStream;
  import java.io.ByteArrayInputStream;
  import java.io.ObjectInputStream;
  import java.io.Serializable;
  
  /**
   * Class that extends Hashtable to demonstrate bug when
   * subclass wraps the values put into the Hashtable.
   */
  public class ReadObject extends Hashtable {
      /**
       * Wraps the values put into MyHashtable objects
       */
      class ValueWrapper implements Serializable {
          private Object mValue;
  
          ValueWrapper(Object value) {
              mValue = value;
          }
  
          Object getValue() {
              return mValue;
          }
      };
  
      public Object get(Object key) {
          ValueWrapper valueWrapper = (ValueWrapper)super.get(key);
          Object value = valueWrapper.getValue();
          if(value instanceof ValueWrapper)
              throw new RuntimeException("Hashtable.get bug");
          return value;
      }
  
      public Object put(Object key, Object value) {
          if(value instanceof ValueWrapper)
              throw new RuntimeException(
                  "Hashtable.put bug: value is already wrapped");
          ValueWrapper valueWrapper = new ValueWrapper(value);
          super.put(key, valueWrapper);
          return value;
      }
  
      private static Object copyObject(Object oldObj) {
          Object newObj = null;
          try {
             //Create a stream in which to serialize the object.
              ByteArrayOutputStream ostream = new ByteArrayOutputStream();
              ObjectOutputStream p = new ObjectOutputStream(ostream);
              //Serialize the object into the stream
              p.writeObject(oldObj);
  
              //Create an input stream from which to deserialize the object
              byte[] byteArray = ostream.toByteArray();
              ByteArrayInputStream istream = new ByteArrayInputStream(byteArray);
              ObjectInputStream q = new ObjectInputStream(istream);
              //Deserialize the object
              newObj = q.readObject();
          } catch (Exception ex) {
              ex.printStackTrace();
          }
          return newObj;
      }
  
      public static void main(String[] args) {
          ReadObject myHashtable = new ReadObject();
          myHashtable.put("key", "value");
          ReadObject myHashtableCopy = (ReadObject)copyObject(myHashtable);
          String value = (String)myHashtableCopy.get("key");
      }
  };
  