1 /*
 2  * Copyright (c) 2016, 2026, 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 8024500 8166446
27  * @library /test/lib
28  * @run testng SingletonIterator
29  */
30 
31 import jdk.test.lib.valueclass.VClass;
32 import java.util.Collections;
33 import java.util.Iterator;
34 import java.util.NoSuchElementException;
35 import java.util.concurrent.atomic.AtomicInteger;
36 import org.testng.annotations.Test;
37 
38 import static org.testng.Assert.assertEquals;
39 import static org.testng.Assert.assertFalse;
40 import static org.testng.Assert.fail;
41 
42 @Test(groups = "unit")
43 public class SingletonIterator {
44     static void assertIteratorExhausted(Iterator<?> it) {
45         assertFalse(it.hasNext());
46         try {
47             it.next();
48             fail("should have thrown NoSuchElementException");
49         } catch (NoSuchElementException success) { }
50         it.forEachRemaining(e -> { throw new AssertionError("action called incorrectly"); });
51     }
52 
53     public void testForEachRemaining() {
54         Iterator<String> it = Collections.singleton("TheOne").iterator();
55         AtomicInteger cnt = new AtomicInteger(0);
56 
57         it.forEachRemaining(s -> {
58             assertEquals("TheOne", s);
59             cnt.incrementAndGet();
60         });
61 
62         assertEquals(cnt.get(), 1);
63         assertIteratorExhausted(it);
64     }
65 
66     static class SingletonException extends RuntimeException { }
67 
68     @Test
69     public void testValueSingletonIterator() {
70         Iterator<VClass> it = Collections.singleton(new VClass(42, new int[] { 42 })).iterator();
71         AtomicInteger cnt = new AtomicInteger(0);
72         it.forEachRemaining(v -> {
73             if (!v.equals(new VClass(42, new int[] { 42 }))) throw new RuntimeException("wrong value");
74             cnt.incrementAndGet();
75         });
76         assertEquals(cnt.get(), 1);
77         assertIteratorExhausted(it);
78     }
79 
80     public void testThrowFromForEachRemaining() {
81         Iterator<String> it = Collections.singleton("TheOne").iterator();
82 
83         try {
84             it.forEachRemaining(s -> { throw new SingletonException(); });
85         } catch (SingletonException ignore) { }
86 
87         assertIteratorExhausted(it);
88     }
89 }