8025173: HashMap.put() replacing an existing key can trigger a resize()
Summary: Ensure that HashMap is not resized if we're just replacing a value
Reviewed-by: alanb, martin
diff --git a/test/java/util/HashMap/ReplaceExisting.java b/test/java/util/HashMap/ReplaceExisting.java
new file mode 100644
index 0000000..81795b3
--- /dev/null
+++ b/test/java/util/HashMap/ReplaceExisting.java
@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8025173
+ * @summary Verify that replacing the value for an existing key does not
+ * corrupt active iterators, in particular due to a resize() occurring and
+ * not updating modCount.
+ * @run main ReplaceExisting
+ */
+
+import java.util.ConcurrentModificationException;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+
+public class ReplaceExisting {
+ /* Number of entries required to trigger a resize for cap=16, load=0.75*/
+ private static int ENTRIES = 13;
+
+ public static void main(String[] args) {
+ for (int i = 0; i <= ENTRIES; i++) {
+ HashMap<Integer,Integer> hm = prepHashMap();
+ testItr(hm, i);
+ }
+ }
+
+ /* Prepare a HashMap that will resize on next put() */
+ private static HashMap<Integer,Integer> prepHashMap() {
+ HashMap<Integer,Integer> hm = new HashMap<>(16, 0.75f);
+ // Add items to one more than the resize threshold
+ for (int i = 0; i < ENTRIES; i++) {
+ hm.put(i*10, i*10);
+ }
+ return hm;
+ }
+
+ /* Iterate hm for elemBeforePut elements, then call put() to replace value
+ * for existing key. With bug 8025173, this will also cause a resize, but
+ * not increase the modCount.
+ * Finish the iteration to check for a corrupt iterator.
+ */
+ private static void testItr(HashMap<Integer,Integer> hm, int elemBeforePut) {
+ if (elemBeforePut > hm.size()) {
+ throw new IllegalArgumentException("Error in test: elemBeforePut must be <= HashMap size");
+ }
+ // Create a copy of the keys
+ HashSet<Integer> keys = new HashSet<>(hm.size());
+ keys.addAll(hm.keySet());
+
+ HashSet<Integer> collected = new HashSet<>(hm.size());
+
+ // Run itr for elemBeforePut items, collecting returned elems
+ Iterator<Integer> itr = hm.keySet().iterator();
+ for (int i = 0; i < elemBeforePut; i++) {
+ Integer retVal = itr.next();
+ if (!collected.add(retVal)) {
+ throw new RuntimeException("Corrupt iterator: key " + retVal + " already encountered");
+ }
+ }
+
+ // Do put() to replace entry (and resize table when bug present)
+ if (null == hm.put(0, 100)) {
+ throw new RuntimeException("Error in test: expected key 0 to be in the HashMap");
+ }
+
+ // Finish itr + collecting returned elems
+ while(itr.hasNext()) {
+ Integer retVal = itr.next();
+ if (!collected.add(retVal)) {
+ throw new RuntimeException("Corrupt iterator: key " + retVal + " already encountered");
+ }
+ }
+
+ // Compare returned elems to original copy of keys
+ if (!keys.equals(collected)) {
+ throw new RuntimeException("Collected keys do not match original set of keys");
+ }
+ }
+}