1 /*
2 * Copyright (c) 2005, 2025, 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 6267846 6275009
27 * @summary Test Collections.nCopies
28 * @author Martin Buchholz
29 */
30
31 import java.util.ArrayList;
32 import java.util.Collections;
33 import java.util.AbstractList;
34 import java.util.List;
35 import java.util.Objects;
36
37 public class NCopies {
38 static volatile int passed = 0, failed = 0;
39
40 static void fail(String msg) {
41 failed++;
42 new AssertionError(msg).printStackTrace();
43 }
44
45 static void pass() {
46 passed++;
47 }
48
49 static void unexpected(Throwable t) {
50 failed++;
51 t.printStackTrace();
52 }
53
54 static void check(boolean condition, String msg) {
55 if (condition)
56 passed++;
57 else
58 fail(msg);
59 }
60
61 static void check(boolean condition) {
62 check(condition, "Assertion failure");
63 }
64
65 private static void checkEmpty(List<String> x) {
66 check(x.isEmpty());
67 check(x.size() == 0);
68 check(x.indexOf("foo") == -1);
69 check(x.lastIndexOf("foo") == -1);
70 check(x.toArray().length == 0);
71 check(x.toArray().getClass() == Object[].class);
72 }
73
74 private static void checkFoos(List<String> x) {
75 check(! x.isEmpty());
76 check(x.indexOf(new String("foo")) == 0);
77 check(x.lastIndexOf(new String("foo")) == x.size()-1);
78 check(x.toArray().length == x.size());
79 check(x.toArray().getClass() == Object[].class);
80 String[] sa = x.toArray(new String[x.size()]);
81 check(sa.getClass() == String[].class);
82 check(sa[0].equals("foo"));
83 check(sa[sa.length-1].equals("foo"));
84 check(x.get(x.size()/2).equals("foo"));
85 checkEmpty(x.subList(x.size()/2, x.size()/2));
86 }
87
88 private static <T> List<T> referenceNCopies(int n, T o) {
89 // A simplest correct implementation of nCopies to compare with the actual optimized implementation
90 return new AbstractList<>() {
91 public int size() { return n; }
92
93 public T get(int index) {
94 Objects.checkIndex(index, n);
95 return o;
96 }
97 };
98 }
99
100 private static void checkHashCode() {
101 int[] sizes = {0, 1, 2, 3, 5, 10, 31, 32, 100, 1000};
102 String[] elements = {null, "non-null"};
103 for (int size : sizes) {
104 for (String element : elements) {
105 int expectedHashCode = referenceNCopies(size, element).hashCode();
106 int actualHashCode = Collections.nCopies(size, element).hashCode();
107 check(expectedHashCode == actualHashCode,
108 "Collections.nCopies(" + size + ", " + element + ").hashCode()");
109 }
110 }
111 }
112
113 private static void checkEquals() {
114 int[][] sizePairs = {{0, 0}, {0, 1}, {1, 0}, {1, 1}, {1, 2}, {2, 1}};
115 String[] elements = {null, "non-null"};
116 for (int[] pair : sizePairs) {
117 for (String element : elements) {
118 boolean equal = pair[0] == pair[1];
119 String msg = "[" + pair[0] + ", " + element + "] <=> [" + pair[1] + ", " + element + "]";
120 check(equal == Collections.nCopies(pair[0], element).equals(Collections.nCopies(pair[1], element)), msg);
121 check(equal == Collections.nCopies(pair[0], element).equals(referenceNCopies(pair[1], element)), msg);
122 check(equal == referenceNCopies(pair[0], element).equals(Collections.nCopies(pair[1], element)), msg);
123 }
124 }
125 List<String> nulls = Collections.nCopies(10, null);
126 List<String> nonNulls = Collections.nCopies(10, "non-null");
127 List<String> nullsButOne = new ArrayList<>(nulls);
128 nullsButOne.set(9, "non-null");
129 List<String> nonNullsButOne = new ArrayList<>(nonNulls);
130 nonNullsButOne.set(9, null);
131 check(!nulls.equals(nonNulls));
132 check(!nulls.equals(nullsButOne));
133 check(!nulls.equals(nonNullsButOne));
134 check(!nonNulls.equals(nonNullsButOne));
135 check(Collections.nCopies(0, null).equals(Collections.nCopies(0, "non-null")));
136 }
137
138 private static void checkReversed() {
139 List<String> copies = Collections.nCopies(10, "content");
140 check(copies.equals(copies.reversed()));
141 List<String> empty = Collections.nCopies(0, "content");
142 check(empty.equals(empty.reversed()));
143 }
144
145 public static void main(String[] args) {
146 try {
147 List<String> empty = Collections.nCopies(0, "foo");
148 checkEmpty(empty);
149 checkEmpty(empty.subList(0,0));
150
151 List<String> foos = Collections.nCopies(42, "foo");
152 check(foos.size() == 42);
153 checkFoos(foos.subList(foos.size()/2, foos.size()-1));
154
155 checkHashCode();
156
157 checkEquals();
158
159 checkReversed();
160
161 } catch (Throwable t) { unexpected(t); }
162
163 System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
164 if (failed > 0) throw new Error("Some tests failed");
165 }
166 }