1 /*
2  * Copyright (c) 2013, 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
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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.
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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
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22  */
23 
24 /**
25  * @test
26  * @bug 8025173
27  * @summary Verify that replacing the value for an existing key does not
28  * corrupt active iterators, in particular due to a resize() occurring and
29  * not updating modCount.
30  * @run main ReplaceExisting
31  */
32 package test.java.util.HashMap;
33 
34 import java.util.ConcurrentModificationException;
35 import java.util.HashMap;
36 import java.util.HashSet;
37 import java.util.Iterator;
38 
39 public class ReplaceExisting {
40     /* Number of entries required to trigger a resize for cap=16, load=0.75*/
41     private static int ENTRIES = 13;
42 
main(String[] args)43     public static void main(String[] args) {
44         for (int i = 0; i <= ENTRIES; i++) {
45             HashMap<Integer,Integer> hm = prepHashMap();
46             testItr(hm, i);
47         }
48     }
49 
50     /* Prepare a HashMap that will resize on next put() */
prepHashMap()51     private static HashMap<Integer,Integer> prepHashMap() {
52         HashMap<Integer,Integer> hm = new HashMap<>(16, 0.75f);
53         // Add items to one more than the resize threshold
54         for (int i = 0; i < ENTRIES; i++) {
55             hm.put(i*10, i*10);
56         }
57         return hm;
58     }
59 
60     /* Iterate hm for elemBeforePut elements, then call put() to replace value
61      * for existing key.  With bug 8025173, this will also cause a resize, but
62      * not increase the modCount.
63      * Finish the iteration to check for a corrupt iterator.
64      */
testItr(HashMap<Integer,Integer> hm, int elemBeforePut)65     private static void testItr(HashMap<Integer,Integer> hm, int elemBeforePut) {
66         if (elemBeforePut > hm.size()) {
67             throw new IllegalArgumentException("Error in test: elemBeforePut must be <= HashMap size");
68         }
69         // Create a copy of the keys
70         HashSet<Integer> keys = new HashSet<>(hm.size());
71         keys.addAll(hm.keySet());
72 
73         HashSet<Integer> collected = new HashSet<>(hm.size());
74 
75         // Run itr for elemBeforePut items, collecting returned elems
76         Iterator<Integer> itr = hm.keySet().iterator();
77         for (int i = 0; i < elemBeforePut; i++) {
78             Integer retVal = itr.next();
79             if (!collected.add(retVal)) {
80                 throw new RuntimeException("Corrupt iterator: key " + retVal + " already encountered");
81             }
82         }
83 
84         // Do put() to replace entry (and resize table when bug present)
85         if (null == hm.put(0, 100)) {
86             throw new RuntimeException("Error in test: expected key 0 to be in the HashMap");
87         }
88 
89         // Finish itr + collecting returned elems
90         while(itr.hasNext()) {
91             Integer retVal = itr.next();
92             if (!collected.add(retVal)) {
93                 throw new RuntimeException("Corrupt iterator: key " + retVal + " already encountered");
94             }
95         }
96 
97         // Compare returned elems to original copy of keys
98         if (!keys.equals(collected)) {
99             throw new RuntimeException("Collected keys do not match original set of keys");
100         }
101     }
102 }
103