Fix FastArrayList iterator to work in thread-safe environments
git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@131802 13f79535-47bb-0310-9956-ffa450edef68
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Stephen Colebourne
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72ed906100
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@ -57,9 +57,10 @@ import java.util.ListIterator;
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* Double-Checked Locking Idiom Is Broken Declaration</a>.</p>
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*
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* @since Commons Collections 1.0
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* @version $Revision: 1.15 $ $Date: 2004/02/18 01:15:42 $
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* @version $Revision: 1.16 $ $Date: 2004/06/23 21:41:49 $
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*
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* @author Craig R. McClanahan
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* @author Stephen Colebourne
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*/
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public class FastArrayList extends ArrayList {
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@ -486,12 +487,20 @@ public class FastArrayList extends ArrayList {
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/**
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* Return an iterator over the elements in this list in proper sequence.
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* <br><br>
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* <strong>IMPLEMENTATION NOTE</strong> - If the list is operating in fast
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* mode, an Iterator is returned, and a structural modification to the
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* list is made, then the Iterator will continue over the previous contents
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* of the list (at the time that the Iterator was created), rather than
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* failing due to concurrent modifications.
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* <p>
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* <b>Thread safety</b><br />
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* The iterator returned is thread-safe ONLY in FAST mode.
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* In slow mode there is no way to synchronize, or make the iterator thread-safe.
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* <p>
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* In fast mode iteration and modification may occur in parallel on different threads,
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* however there is a restriction. Modification must be EITHER via the Iterator
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* interface methods OR the List interface. If a mixture of modification
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* methods is used a ConcurrentModificationException is thrown from the iterator
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* modification method. If the List modification methods are used the changes are
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* NOT visible in the iterator (it shows the list contents at the time the iterator
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* was created).
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*
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* @return the iterator
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*/
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public Iterator iterator() {
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if (fast) {
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@ -524,7 +533,20 @@ public class FastArrayList extends ArrayList {
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/**
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* Return an iterator of the elements of this list, in proper sequence.
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* See the implementation note on <code>iterator()</code>.
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* <p>
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* <b>Thread safety</b><br />
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* The iterator returned is thread-safe ONLY in FAST mode.
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* In slow mode there is no way to synchronize, or make the iterator thread-safe.
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* <p>
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* In fast mode iteration and modification may occur in parallel on different threads,
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* however there is a restriction. Modification must be EITHER via the Iterator
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* interface methods OR the List interface. If a mixture of modification
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* methods is used a ConcurrentModificationException is thrown from the iterator
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* modification method. If the List modification methods are used the changes are
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* NOT visible in the iterator (it shows the list contents at the time the iterator
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* was created).
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*
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* @return the list iterator
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*/
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public ListIterator listIterator() {
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if (fast) {
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@ -538,10 +560,21 @@ public class FastArrayList extends ArrayList {
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/**
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* Return an iterator of the elements of this list, in proper sequence,
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* starting at the specified position.
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* See the implementation note on <code>iterator()</code>.
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* <p>
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* <b>Thread safety</b><br />
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* The iterator returned is thread-safe ONLY in FAST mode.
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* In slow mode there is no way to synchronize, or make the iterator thread-safe.
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* <p>
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* In fast mode iteration and modification may occur in parallel on different threads,
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* however there is a restriction. Modification must be EITHER via the Iterator
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* interface methods OR the List interface. If a mixture of modification
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* methods is used a ConcurrentModificationException is thrown from the iterator
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* modification method. If the List modification methods are used the changes are
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* NOT visible in the iterator (it shows the list contents at the time the iterator
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* was created).
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*
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* @param index The starting position of the iterator to return
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*
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* @return the list iterator
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* @exception IndexOutOfBoundsException if the index is out of range
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*/
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public ListIterator listIterator(int index) {
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@ -1205,8 +1238,9 @@ public class FastArrayList extends ArrayList {
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int i = nextIndex();
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get().add(i, o);
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last++;
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expected = list;
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iter = get().listIterator(i + 1);
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lastReturnedIndex = 1;
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lastReturnedIndex = -1;
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}
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}
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@ -1239,34 +1273,28 @@ public class FastArrayList extends ArrayList {
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}
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public boolean hasNext() {
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checkMod();
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return iter.hasNext();
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}
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public Object next() {
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checkMod();
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lastReturnedIndex = iter.nextIndex();
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return iter.next();
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}
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public boolean hasPrevious() {
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checkMod();
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return iter.hasPrevious();
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}
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public Object previous() {
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checkMod();
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lastReturnedIndex = iter.previousIndex();
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return iter.previous();
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}
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public int previousIndex() {
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checkMod();
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return iter.previousIndex();
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}
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public int nextIndex() {
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checkMod();
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return iter.nextIndex();
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}
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@ -1295,6 +1323,7 @@ public class FastArrayList extends ArrayList {
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checkMod();
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int i = nextIndex();
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get().add(i, o);
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expected = list;
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iter = get().listIterator(i + 1);
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lastReturnedIndex = -1;
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}
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@ -16,14 +16,17 @@
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package org.apache.commons.collections;
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import java.util.ArrayList;
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import java.util.ConcurrentModificationException;
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import java.util.Iterator;
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import java.util.List;
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import java.util.ListIterator;
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import junit.framework.Test;
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/**
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* Test FastArrayList implementation in <strong>fast</strong> mode.
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*
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* @version $Revision: 1.9 $ $Date: 2004/02/18 01:20:35 $
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* @version $Revision: 1.10 $ $Date: 2004/06/23 21:41:49 $
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*
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* @author Jason van Zyl
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*/
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@ -51,13 +54,52 @@ public class TestFastArrayList1 extends TestFastArrayList {
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fal.setFast(true);
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return (fal);
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}
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public String[] ignoredTests() {
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// subList impl result in...
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return new String[] {
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"TestFastArrayList1.bulkTestSubList.bulkTestListIterator.testAddThenSet",
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"TestFastArrayList1.bulkTestSubList.bulkTestListIterator.testAddThenRemove",
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};
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public void testIterateModify1() {
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List list = makeEmptyList();
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list.add("A");
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list.add("B");
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list.add("C");
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assertEquals(3, list.size());
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Iterator it = list.iterator();
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assertEquals("A", it.next());
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assertEquals(3, list.size());
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list.add(1, "Z");
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assertEquals(4, list.size());
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assertEquals("B", it.next());
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assertEquals("C", it.next());
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assertEquals(false, it.hasNext());
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}
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public void testIterateModify2() {
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List list = makeEmptyList();
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list.add("A");
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list.add("B");
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list.add("C");
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assertEquals(3, list.size());
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ListIterator it = list.listIterator();
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assertEquals("A", it.next());
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it.add("M"); // change via Iterator interface
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assertEquals(4, list.size());
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list.add(2, "Z"); // change via List interface
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assertEquals(5, list.size());
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assertEquals("B", it.next());
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try {
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it.set("N"); // fails as previously changed via List interface
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fail();
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} catch (ConcurrentModificationException ex) {}
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try {
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it.remove();
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fail();
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} catch (ConcurrentModificationException ex) {}
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try {
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it.add("N");
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fail();
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} catch (ConcurrentModificationException ex) {}
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assertEquals("C", it.next());
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assertEquals(false, it.hasNext());
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}
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}
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