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/* |
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* Copyright (c) 2007, 2017, 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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/* |
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* @test |
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* @bug 6499848 |
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* @library /test/lib |
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* @run main GCDuringIteration |
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* @summary Check that iterators work properly in the presence of |
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* concurrent finalization and removal of elements. |
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* @key randomness |
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*/ |
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|
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import static java.util.concurrent.TimeUnit.SECONDS; |
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|
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import java.lang.ref.WeakReference; |
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import java.util.Arrays; |
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import java.util.Iterator; |
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import java.util.Map; |
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import java.util.NoSuchElementException; |
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import java.util.Random; |
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import java.util.WeakHashMap; |
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import java.util.concurrent.CountDownLatch; |
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import java.util.function.BooleanSupplier; |
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import jdk.test.lib.RandomFactory; |
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|
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public class GCDuringIteration { |
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|
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/** No guarantees, but effective in practice. */ |
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static void forceFullGc() { |
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CountDownLatch finalizeDone = new CountDownLatch(1); |
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WeakReference<?> ref = new WeakReference<Object>(new Object() { |
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protected void finalize() { finalizeDone.countDown(); }}); |
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try { |
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for (int i = 0; i < 10; i++) { |
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System.gc(); |
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if (finalizeDone.await(1L, SECONDS) && ref.get() == null) { |
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System.runFinalization(); // try to pick up stragglers |
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return; |
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} |
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} |
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} catch (InterruptedException unexpected) { |
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throw new AssertionError("unexpected InterruptedException"); |
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} |
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throw new AssertionError("failed to do a \"full\" gc"); |
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} |
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|
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static void gcAwait(BooleanSupplier s) { |
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for (int i = 0; i < 10; i++) { |
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if (s.getAsBoolean()) |
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return; |
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forceFullGc(); |
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} |
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throw new AssertionError("failed to satisfy condition"); |
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} |
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|
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// A class with the traditional pessimal hashCode implementation, |
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// to ensure that all instances end up in the same bucket. |
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static class Foo { public int hashCode() { return 42; }} |
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|
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<K,V> void put(Map<K,V> map, K k, V v) { |
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check(! map.containsKey(k)); |
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equal(map.get(k), null); |
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equal(map.put(k, v), null); |
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equal(map.get(k), v); |
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check(map.containsKey(k)); |
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equal(map.put(k, v), v); |
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equal(map.get(k), v); |
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check(map.containsKey(k)); |
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check(! map.isEmpty()); |
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equal(map.keySet().iterator().next(), k); |
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equal(map.values().iterator().next(), v); |
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} |
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|
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static final Random rnd = RandomFactory.getRandom(); |
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|
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void checkIterator(final Iterator<Map.Entry<Foo, Integer>> it, int first) { |
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for (int i = first; i >= 0; --i) { |
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if (rnd.nextBoolean()) check(it.hasNext()); |
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equal(it.next().getValue(), i); |
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} |
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if (rnd.nextBoolean()) { |
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try { |
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it.next(); |
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throw new AssertionError("should throw"); |
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} catch (NoSuchElementException success) {} |
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} |
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|
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if (rnd.nextBoolean()) |
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check(! it.hasNext()); |
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} |
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|
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<K,V> V firstValue(Map<K,V> map) { |
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return map.values().iterator().next(); |
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} |
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|
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void test(String[] args) throws Throwable { |
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final int n = 10; |
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// Create array of strong refs |
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final Foo[] foos = new Foo[2*n]; |
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final Map<Foo,Integer> map = new WeakHashMap<>(foos.length); |
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check(map.isEmpty()); |
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equal(map.size(), 0); |
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|
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for (int i = 0; i < foos.length; i++) { |
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Foo foo = new Foo(); |
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foos[i] = foo; |
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put(map, foo, i); |
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} |
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equal(map.size(), foos.length); |
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|
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{ |
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int first = firstValue(map); |
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final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator(); |
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foos[first] = null; |
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gcAwait(() -> map.size() == first); |
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checkIterator(it, first-1); |
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equal(map.size(), first); |
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equal(firstValue(map), first-1); |
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} |
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|
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{ |
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int first = firstValue(map); |
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final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator(); |
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it.next(); // protects first entry |
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System.out.println(map.values()); |
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int oldSize = map.size(); |
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foos[first] = null; |
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forceFullGc(); |
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equal(map.size(), oldSize); |
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System.out.println(map.values()); |
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checkIterator(it, first-1); |
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// first entry no longer protected |
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gcAwait(() -> map.size() == first); |
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equal(firstValue(map), first-1); |
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} |
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|
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{ |
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int first = firstValue(map); |
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final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator(); |
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it.next(); // protects first entry |
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System.out.println(map.values()); |
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foos[first] = foos[first-1] = null; |
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gcAwait(() -> map.size() == first); |
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equal(firstValue(map), first); |
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System.out.println(map.values()); |
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checkIterator(it, first-2); |
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// first entry no longer protected |
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gcAwait(() -> map.size() == first-1); |
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equal(firstValue(map), first-2); |
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} |
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|
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{ |
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int first = firstValue(map); |
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final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator(); |
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it.next(); // protects first entry |
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it.hasNext(); // protects second entry |
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System.out.println(map.values()); |
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int oldSize = map.size(); |
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foos[first] = foos[first-1] = null; |
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forceFullGc(); |
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equal(map.size(), oldSize); |
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equal(firstValue(map), first); |
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System.out.println(map.values()); |
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checkIterator(it, first-1); |
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// first entry no longer protected |
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gcAwait(() -> map.size() == first-1); |
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equal(firstValue(map), first-2); |
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} |
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|
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{ |
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int first = firstValue(map); |
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final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator(); |
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it.next(); // protects first entry |
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System.out.println(map.values()); |
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equal(map.size(), first+1); |
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foos[first] = foos[first-1] = null; |
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gcAwait(() -> map.size() == first); |
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it.remove(); |
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equal(firstValue(map), first-2); |
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equal(map.size(), first-1); |
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System.out.println(map.values()); |
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checkIterator(it, first-2); |
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// first entry no longer protected |
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gcAwait(() -> map.size() == first-1); |
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equal(firstValue(map), first-2); |
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} |
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|
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{ |
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int first = firstValue(map); |
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final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator(); |
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it.next(); // protects first entry |
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it.remove(); |
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it.hasNext(); // protects second entry |
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System.out.println(map.values()); |
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equal(map.size(), first); |
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foos[first] = foos[first-1] = null; |
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forceFullGc(); |
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equal(firstValue(map), first-1); |
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equal(map.size(), first); |
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System.out.println(map.values()); |
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checkIterator(it, first-1); |
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gcAwait(() -> map.size() == first-1); |
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equal(firstValue(map), first-2); |
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} |
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|
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{ |
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int first = firstValue(map); |
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final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator(); |
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it.hasNext(); // protects first entry |
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Arrays.fill(foos, null); |
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gcAwait(() -> map.size() == 1); |
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System.out.println(map.values()); |
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equal(it.next().getValue(), first); |
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check(! it.hasNext()); |
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gcAwait(() -> map.size() == 0); |
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check(map.isEmpty()); |
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} |
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} |
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|
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//--------------------- Infrastructure --------------------------- |
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volatile int passed = 0, failed = 0; |
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void pass() {passed++;} |
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void fail() {failed++; Thread.dumpStack();} |
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void fail(String msg) {System.err.println(msg); fail();} |
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void unexpected(Throwable t) {failed++; t.printStackTrace();} |
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void check(boolean cond) {if (cond) pass(); else fail();} |
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void equal(Object x, Object y) { |
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if (x == null ? y == null : x.equals(y)) pass(); |
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else fail(x + " not equal to " + y);} |
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public static void main(String[] args) throws Throwable { |
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new GCDuringIteration().instanceMain(args);} |
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void instanceMain(String[] args) throws Throwable { |
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try {test(args);} catch (Throwable t) {unexpected(t);} |
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System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed); |
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if (failed > 0) throw new AssertionError("Some tests failed");} |
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} |
