content: /*
   * Copyright (c) 1996, 2004, 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
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.io;
  
  import java.io.ObjectOutput;
  import java.io.ObjectInput;
  
  /**
   * Only the identity of the class of an Externalizable instance is
   * written in the serialization stream and it is the responsibility
   * of the class to save and restore the contents of its instances.
   *
   * The writeExternal and readExternal methods of the Externalizable
   * interface are implemented by a class to give the class complete
   * control over the format and contents of the stream for an object
   * and its supertypes. These methods must explicitly
   * coordinate with the supertype to save its state. These methods supersede
   * customized implementations of writeObject and readObject methods.<br>
   *
   * Object Serialization uses the Serializable and Externalizable
   * interfaces.  Object persistence mechanisms can use them as well.  Each
   * object to be stored is tested for the Externalizable interface. If
   * the object supports Externalizable, the writeExternal method is called. If the
   * object does not support Externalizable and does implement
   * Serializable, the object is saved using
   * ObjectOutputStream. <br> When an Externalizable object is
   * reconstructed, an instance is created using the public no-arg
   * constructor, then the readExternal method called.  Serializable
   * objects are restored by reading them from an ObjectInputStream.<br>
   *
   * An Externalizable instance can designate a substitution object via
   * the writeReplace and readResolve methods documented in the Serializable
   * interface.<br>
   *
   * @author  unascribed
   * @see ObjectOutputStream
   * @see ObjectInputStream
   * @see ObjectOutput
   * @see ObjectInput
   * @see Serializable
   * @since   JDK1.1
   */
  public interface Externalizable extends Serializable {
      /**
       * The object implements the writeExternal method to save its contents
       * by calling the methods of DataOutput for its primitive values or
       * calling the writeObject method of ObjectOutput for objects, strings,
       * and arrays.
       *
       * @serialData Overriding methods should use this tag to describe
       *             the data layout of this Externalizable object.
       *             List the sequence of element types and, if possible,
       *             relate the element to a public/protected field and/or
       *             method of this Externalizable class.
       *
       * @param out the stream to write the object to
       * @exception IOException Includes any I/O exceptions that may occur
       */
      void writeExternal(ObjectOutput out) throws IOException;
  
      /**
       * The object implements the readExternal method to restore its
       * contents by calling the methods of DataInput for primitive
       * types and readObject for objects, strings and arrays.  The
       * readExternal method must read the values in the same sequence
       * and with the same types as were written by writeExternal.
       *
       * @param in the stream to read data from in order to restore the object
       * @exception IOException if I/O errors occur
       * @exception ClassNotFoundException If the class for an object being
       *              restored cannot be found.
       */
      void readExternal(ObjectInput in) throws IOException, ClassNotFoundException;
  }
  