1 /*
 2  * Copyright (c) 2023, 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     8294693
27  * @summary Basic test for Collections.shuffle
28  * @key     randomness

29  */
30 

31 import java.util.ArrayList;
32 import java.util.Collections;
33 import java.util.LinkedList;
34 import java.util.List;
35 import java.util.Random;
36 import java.util.function.Consumer;
37 import java.util.random.RandomGenerator;
38 
39 public class Shuffle {
40     static final int N = 100;
41 
42     public static void main(String[] args) {
43         test(new ArrayList<>());
44         test(new LinkedList<>());

45     }
46 
47     static void test(List<Integer> list) {
48         for (int i = 0; i < N; i++) {
49             list.add(i);
50         }
51         Collections.shuffle(list);
52         if (list.size() != N) {
53             throw new RuntimeException(list.getClass() + ": size " + list.size() + " != " + N);
54         }
55         for (int i = 0; i < N; i++) {
56             if (!list.contains(i)) {
57                 throw new RuntimeException(list.getClass() + ": does not contain " + i);
58             }
59         }
60         checkRandom(list, l -> Collections.shuffle(l, new Random(1)));
61         RandomGenerator.JumpableGenerator generator = RandomGenerator.JumpableGenerator.of("Xoshiro256PlusPlus");
62         checkRandom(list, l -> Collections.shuffle(l, generator.copy()));
63     }
64 










65     private static void checkRandom(List<Integer> list, Consumer<List<?>> randomizer) {
66         list.sort(null);
67         randomizer.accept(list);
68         ArrayList<Integer> copy = new ArrayList<>(list);
69         list.sort(null);
70         if (list.equals(copy)) {
71             // Assume that at least one pair of elements must be reordered during shuffle
72             throw new RuntimeException(list.getClass() + ": list is not shuffled");
73         }
74         randomizer.accept(list);
75         if (!list.equals(copy)) {
76             throw new RuntimeException(list.getClass() + ": " + list + " != " + copy);
77         }
78     }
79 }
--- EOF ---