1 /*
   2  * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved.
   3  * 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  * 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  */
  23 
  24 /*
  25  * @test
  26  * @bug     4684279 7129185
  27  * @summary Empty utility collections should be singletons
  28  * @author  Josh Bloch
  29  * @run testng EmptyCollectionSerialization
  30  */
  31 
  32 import java.util.*;
  33 import java.util.function.Supplier;
  34 import java.io.*;
  35 import org.testng.annotations.Test;
  36 import org.testng.annotations.DataProvider;
  37 
  38 import static org.testng.Assert.fail;
  39 import static org.testng.Assert.assertSame;
  40 
  41 public class EmptyCollectionSerialization {
  42     private static Object patheticDeepCopy(Object o) throws Exception {
  43         // Serialize
  44         ByteArrayOutputStream bos = new ByteArrayOutputStream();
  45         ObjectOutputStream oos = new ObjectOutputStream(bos);
  46         oos.writeObject(o);
  47         byte[] serializedForm = bos.toByteArray();
  48 
  49         // Deserialize
  50         InputStream is = new ByteArrayInputStream(serializedForm);
  51         ObjectInputStream ois = new ObjectInputStream(is);
  52         return ois.readObject();
  53     }
  54 
  55     @Test(dataProvider="SerializableSingletons")
  56     public static void serializableSingletons(String description, Supplier<Object> o) {
  57         try {
  58             Object singleton = o.get();
  59             assertSame(o.get(), singleton, description + ": broken Supplier not returning singleton");
  60             Object copy = patheticDeepCopy(singleton);
  61             assertSame( copy, singleton, description + ": " +
  62                 copy.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(copy)) +
  63                 " is not the singleton " +
  64                 singleton.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(singleton)));
  65         } catch(Exception all) {
  66             fail(description + ": Unexpected Exception", all);
  67         }
  68     }
  69 
  70     @DataProvider(name = "SerializableSingletons", parallel = true)
  71     public static Iterator<Object[]> navigableMapProvider() {
  72         return makeSingletons().iterator();
  73     }
  74 
  75     public static Collection<Object[]> makeSingletons() {
  76         return Arrays.asList(
  77             new Object[]{"Collections.EMPTY_LIST",
  78                 (Supplier) () -> {return Collections.EMPTY_LIST;}},
  79             new Object[]{"Collections.EMPTY_MAP",
  80                 (Supplier) () -> {return Collections.EMPTY_MAP;}},
  81             new Object[]{"Collections.EMPTY_SET",
  82                 (Supplier) () -> {return Collections.EMPTY_SET;}},
  83             new Object[]{"Collections.singletonMap()",
  84                 (Supplier) () -> {return Collections.emptyList();}},
  85             new Object[]{"Collections.emptyMap()",
  86                 (Supplier) () -> {return Collections.emptyMap();}},
  87             new Object[]{"Collections.emptySet()",
  88                 (Supplier) () -> {return Collections.emptySet();}},
  89             new Object[]{"Collections.emptySortedSet()",
  90                 (Supplier) () -> {return Collections.emptySortedSet();}},
  91             new Object[]{"Collections.emptySortedMap()",
  92                 (Supplier) () -> {return Collections.emptySortedMap();}},
  93             new Object[]{"Collections.emptyNavigableSet()",
  94                 (Supplier) () -> {return Collections.emptyNavigableSet();}},
  95             new Object[]{"Collections.emptyNavigableMap()",
  96                 (Supplier) () -> {return Collections.emptyNavigableMap();}}
  97             );
  98     }
  99 }