80 lines
2.8 KiB
Java
80 lines
2.8 KiB
Java
/*
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* Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* @test
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* @bug 8294693
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* @summary Basic test for Collections.shuffle
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* @key randomness
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*/
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.Random;
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import java.util.function.Consumer;
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import java.util.random.RandomGenerator;
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public class Shuffle {
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static final int N = 100;
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public static void main(String[] args) {
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test(new ArrayList<>());
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test(new LinkedList<>());
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}
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static void test(List<Integer> list) {
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for (int i = 0; i < N; i++) {
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list.add(i);
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}
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Collections.shuffle(list);
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if (list.size() != N) {
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throw new RuntimeException(list.getClass() + ": size " + list.size() + " != " + N);
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}
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for (int i = 0; i < N; i++) {
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if (!list.contains(i)) {
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throw new RuntimeException(list.getClass() + ": does not contain " + i);
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}
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}
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checkRandom(list, l -> Collections.shuffle(l, new Random(1)));
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RandomGenerator.JumpableGenerator generator = RandomGenerator.JumpableGenerator.of("Xoshiro256PlusPlus");
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checkRandom(list, l -> Collections.shuffle(l, generator.copy()));
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}
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private static void checkRandom(List<Integer> list, Consumer<List<?>> randomizer) {
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list.sort(null);
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randomizer.accept(list);
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ArrayList<Integer> copy = new ArrayList<>(list);
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list.sort(null);
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if (list.equals(copy)) {
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// Assume that at least one pair of elements must be reordered during shuffle
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throw new RuntimeException(list.getClass() + ": list is not shuffled");
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}
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randomizer.accept(list);
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if (!list.equals(copy)) {
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throw new RuntimeException(list.getClass() + ": " + list + " != " + copy);
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}
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}
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}
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