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
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 }
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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 }
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