/*

 * Copyright (c) 2002, 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.

 *

 * 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.

 */

/*

 * @test

 * @bug     4684279

 * @summary Empty utility collections should be singletons

 * @author  Josh Bloch

 */

import java.util.*;

import java.io.*;

public class EmptyCollectionSerialization {

    private static Object patheticDeepCopy(Object o) throws Exception {

        // Serialize

        ByteArrayOutputStream bos = new ByteArrayOutputStream();

        ObjectOutputStream oos = new ObjectOutputStream(bos);

        oos.writeObject(o);

        byte[] serializedForm = bos.toByteArray();

        // Deserialize

        InputStream is = new ByteArrayInputStream(serializedForm);

        ObjectInputStream ois = new ObjectInputStream(is);

        return ois.readObject();

    }

    private static boolean isSingleton(Object o) throws Exception {

        return patheticDeepCopy(o) == o;

    }

    public static void main(String[] args) throws Exception {

        if (!isSingleton(Collections.EMPTY_SET))

            throw new Exception("EMPTY_SET");

        if (!isSingleton(Collections.EMPTY_LIST))

            throw new Exception("EMPTY_LIST");

        if (!isSingleton(Collections.EMPTY_MAP))

            throw new Exception("EMPTY_MAP");

    }

}