util/Collections/EmptyCollectionSerialization.java

/*
 * 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");
    }
}
Revision:	1.2
Committed:	Sun Sep 5 21:32:19 2010 UTC (13 years, 8 months ago) by jsr166
Branch:	MAIN
CVS Tags:	release-1_7_0
Changes since 1.1:	+4 -4 lines
Log Message:	Update legal notices to Oracle wording
#	User	Rev	Content
1	jsr166	1.1	/*
2	jsr166	1.2	* Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved.
3	jsr166	1.1	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4			*
5			* This code is free software; you can redistribute it and/or modify it
6			* under the terms of the GNU General Public License version 2 only, as
7			* published by the Free Software Foundation.
8			*
9			* This code is distributed in the hope that it will be useful, but WITHOUT
10			* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11			* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12			* version 2 for more details (a copy is included in the LICENSE file that
13			* accompanied this code).
14			*
15			* You should have received a copy of the GNU General Public License version
16			* 2 along with this work; if not, write to the Free Software Foundation,
17			* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18			*
19	jsr166	1.2	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20			* or visit www.oracle.com if you need additional information or have any
21			* questions.
22	jsr166	1.1	*/
23
24			/*
25			* @test
26			* @bug 4684279
27			* @summary Empty utility collections should be singletons
28			* @author Josh Bloch
29			*/
30
31			import java.util.*;
32			import java.io.*;
33
34			public class EmptyCollectionSerialization {
35			private static Object patheticDeepCopy(Object o) throws Exception {
36			// Serialize
37			ByteArrayOutputStream bos = new ByteArrayOutputStream();
38			ObjectOutputStream oos = new ObjectOutputStream(bos);
39			oos.writeObject(o);
40			byte[] serializedForm = bos.toByteArray();
41
42			// Deserialize
43			InputStream is = new ByteArrayInputStream(serializedForm);
44			ObjectInputStream ois = new ObjectInputStream(is);
45			return ois.readObject();
46			}
47
48			private static boolean isSingleton(Object o) throws Exception {
49			return patheticDeepCopy(o) == o;
50			}
51
52			public static void main(String[] args) throws Exception {
53			if (!isSingleton(Collections.EMPTY_SET))
54			throw new Exception("EMPTY_SET");
55			if (!isSingleton(Collections.EMPTY_LIST))
56			throw new Exception("EMPTY_LIST");
57			if (!isSingleton(Collections.EMPTY_MAP))
58			throw new Exception("EMPTY_MAP");
59			}
60			}