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8234423: Modifying ArrayList.subList().subList() resets modCount of s…

…ubList

Reviewed-by: rriggs
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Ivan Gerasimov
Ivan Gerasimov committed Jan 14, 2020
1 parent 27d782b commit 1507a1fb67724237fadce2e9ca7e707bf865300a
@@ -1133,7 +1133,7 @@ private SubList(SubList<E> parent, int fromIndex, int toIndex) {
this.parent = parent;
this.offset = parent.offset + fromIndex;
this.size = toIndex - fromIndex;
this.modCount = root.modCount;
this.modCount = parent.modCount;
}

public E set(int index, E element) {
@@ -1286,7 +1286,7 @@ public boolean contains(Object o) {
return new ListIterator<E>() {
int cursor = index;
int lastRet = -1;
int expectedModCount = root.modCount;
int expectedModCount = SubList.this.modCount;

public boolean hasNext() {
return cursor != SubList.this.size;
@@ -1330,7 +1330,7 @@ public void forEachRemaining(Consumer<? super E> action) {
final Object[] es = root.elementData;
if (offset + i >= es.length)
throw new ConcurrentModificationException();
for (; i < size && modCount == expectedModCount; i++)
for (; i < size && root.modCount == expectedModCount; i++)
action.accept(elementAt(es, offset + i));
// update once at end to reduce heap write traffic
cursor = i;
@@ -1356,7 +1356,7 @@ public void remove() {
SubList.this.remove(lastRet);
cursor = lastRet;
lastRet = -1;
expectedModCount = root.modCount;
expectedModCount = SubList.this.modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
@@ -1382,7 +1382,7 @@ public void add(E e) {
SubList.this.add(i, e);
cursor = i + 1;
lastRet = -1;
expectedModCount = root.modCount;
expectedModCount = SubList.this.modCount;
} catch (IndexOutOfBoundsException ex) {
throw new ConcurrentModificationException();
}
@@ -0,0 +1,68 @@
/*
* Copyright (c) 2019, 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 8234423
* @summary Modifying ArrayList.subList().subList() resets modCount of subList
*/

import java.util.ArrayList;
import java.util.ConcurrentModificationException;

public class SubListModCount {
public static void main(String[] args) {
int failures = 0;
var root = new ArrayList<Integer>();
var subList = root.subList(0, 0);
root.add(42);
try {
subList.size();
failures++;
System.out.println("Accessing subList");
} catch (ConcurrentModificationException expected) {
}
var subSubList = subList.subList(0, 0);
try {
subSubList.size();
failures++;
System.out.println("Accessing subList.subList");
} catch (ConcurrentModificationException expected) {
}
try {
subSubList.add(42);
failures++;
System.out.println("Modifying subList.subList");
} catch (ConcurrentModificationException expected) {
}
try {
subList.size();
failures++;
System.out.println("Accessing subList again");
} catch (ConcurrentModificationException expected) {
}
if (failures > 0) {
throw new AssertionError(failures + " tests failed");
}
}
}

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