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evandorevandor
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Merge pull request eugenp#3243 from shouvikbhattacharya/BAEL-1433
Bael 1433: Guide to TreeSet in Java
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‎core-java/src/test/java/com/baeldung/collection/WhenUsingTreeSet.java‎

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package com.baeldung.collection;
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import java.util.Comparator;
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import java.util.ConcurrentModificationException;
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import java.util.Iterator;
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import java.util.NavigableSet;
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import java.util.Set;
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import java.util.SortedSet;
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import java.util.TreeSet;
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import org.junit.Assert;
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import org.junit.Test;
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public class WhenUsingTreeSet {
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private static class Element {
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private Integer id;
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public Integer getId() {
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return id;
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}
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public void setId(Integer id) {
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this.id = id;
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}
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@Override
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public String toString() {
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// TODO Auto-generated method stub
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return id.toString();
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}
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}
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private Comparator<Element> comparator = (ele1, ele2) -> {
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return ele1.getId()
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.compareTo(ele2.getId());
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};
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@Test
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public void whenAddingElement_shouldAddElement() {
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Set<String> treeSet = new TreeSet<>();
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Assert.assertTrue(treeSet.add("String Added"));
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}
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@Test
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public void whenCheckingForElement_shouldSearchForElement() {
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Set<String> treeSetContains = new TreeSet<>();
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treeSetContains.add("String Added");
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Assert.assertTrue(treeSetContains.contains("String Added"));
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}
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@Test
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public void whenRemovingElement_shouldRemoveElement() {
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Set<String> removeFromTreeSet = new TreeSet<>();
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removeFromTreeSet.add("String Added");
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Assert.assertTrue(removeFromTreeSet.remove("String Added"));
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}
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@Test
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public void whenClearingTreeSet_shouldClearTreeSet() {
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Set<String> clearTreeSet = new TreeSet<>();
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clearTreeSet.add("String Added");
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clearTreeSet.clear();
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Assert.assertTrue(clearTreeSet.isEmpty());
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}
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@Test
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public void whenCheckingTheSizeOfTreeSet_shouldReturnThesize() {
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Set<String> treeSetSize = new TreeSet<>();
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treeSetSize.add("String Added");
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Assert.assertEquals(1, treeSetSize.size());
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}
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@Test
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public void whenCheckingForEmptyTreeSet_shouldCheckForEmpty() {
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Set<String> emptyTreeSet = new TreeSet<>();
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Assert.assertTrue(emptyTreeSet.isEmpty());
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}
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@Test
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public void whenIteratingTreeSet_shouldIterateTreeSetInAscendingOrder() {
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Set<String> treeSet = new TreeSet<>();
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treeSet.add("First");
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treeSet.add("Second");
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treeSet.add("Third");
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Iterator<String> itr = treeSet.iterator();
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while (itr.hasNext()) {
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System.out.println(itr.next());
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}
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}
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@Test
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public void whenIteratingTreeSet_shouldIterateTreeSetInDescendingOrder() {
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TreeSet<String> treeSet = new TreeSet<>();
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treeSet.add("First");
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treeSet.add("Second");
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treeSet.add("Third");
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Iterator<String> itr = treeSet.descendingIterator();
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while (itr.hasNext()) {
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System.out.println(itr.next());
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}
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}
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@Test(expected = ConcurrentModificationException.class)
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public void whenModifyingTreeSetWhileIterating_shouldThrowException() {
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Set<String> treeSet = new TreeSet<>();
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treeSet.add("First");
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treeSet.add("Second");
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treeSet.add("Third");
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Iterator<String> itr = treeSet.iterator();
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while (itr.hasNext()) {
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itr.next();
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treeSet.remove("Second");
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}
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}
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@Test
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public void whenRemovingElementUsingIterator_shouldRemoveElement() {
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Set<String> treeSet = new TreeSet<>();
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treeSet.add("First");
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treeSet.add("Second");
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treeSet.add("Third");
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Iterator<String> itr = treeSet.iterator();
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while (itr.hasNext()) {
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String element = itr.next();
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if (element.equals("Second"))
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itr.remove();
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}
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Assert.assertEquals(2, treeSet.size());
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}
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@Test(expected = NullPointerException.class)
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public void whenAddingNullToNonEmptyTreeSet_shouldThrowException() {
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Set<String> treeSet = new TreeSet<>();
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treeSet.add("First");
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treeSet.add(null);
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}
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@Test
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public void whenCheckingFirstElement_shouldReturnFirstElement() {
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TreeSet<String> treeSet = new TreeSet<>();
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treeSet.add("First");
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Assert.assertEquals("First", treeSet.first());
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}
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@Test
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public void whenCheckingLastElement_shouldReturnLastElement() {
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TreeSet<String> treeSet = new TreeSet<>();
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treeSet.add("First");
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treeSet.add("Last");
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Assert.assertEquals("Last", treeSet.last());
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}
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@Test
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public void whenUsingComparator_shouldSortAndInsertElements() {
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Set<Element> treeSet = new TreeSet<>(comparator);
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Element ele1 = new Element();
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ele1.setId(100);
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Element ele2 = new Element();
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ele2.setId(200);
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treeSet.add(ele1);
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treeSet.add(ele2);
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System.out.println(treeSet);
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}
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@Test
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public void whenUsingHeadSet_shouldReturnElementsLessThanSpecifiedElement() {
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Set<Element> treeSet = new TreeSet<>(comparator);
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Element ele1 = new Element();
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ele1.setId(100);
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Element ele2 = new Element();
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ele2.setId(200);
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treeSet.add(ele1);
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treeSet.add(ele2);
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System.out.println(treeSet);
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}
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@Test
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public void whenUsingSubSet_shouldReturnSubSetElements() {
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SortedSet<Integer> treeSet = new TreeSet<>();
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treeSet.add(1);
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treeSet.add(2);
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treeSet.add(3);
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treeSet.add(4);
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treeSet.add(5);
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treeSet.add(6);
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Set<Integer> subSet = treeSet.subSet(2, 6);
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System.out.println(subSet);
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}
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@Test
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public void whenUsingHeadSet_shouldReturnHeadSetElements() {
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SortedSet<Integer> treeSet = new TreeSet<>();
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treeSet.add(1);
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treeSet.add(2);
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treeSet.add(3);
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treeSet.add(4);
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treeSet.add(5);
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treeSet.add(6);
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Set<Integer> subSet = treeSet.headSet(6);
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Assert.assertEquals(subSet, treeSet.subSet(1, 6));
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}
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@Test
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public void whenUsingTailSet_shouldReturnTailSetElements() {
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NavigableSet<Integer> treeSet = new TreeSet<>();
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treeSet.add(1);
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treeSet.add(2);
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treeSet.add(3);
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treeSet.add(4);
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treeSet.add(5);
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treeSet.add(6);
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Set<Integer> subSet = treeSet.tailSet(3);
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Assert.assertEquals(subSet, treeSet.subSet(3, true, 6, true));
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}
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}

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