/*
 * 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
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 */

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 java.io.ObjectOutputStream
 * @see java.io.ObjectInputStream
 * @see java.io.ObjectOutput
 * @see java.io.ObjectInput
 * @see java.io.Serializable
 * @since 1.1
 */
public interface Externalizable extends java.io.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;
}