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Merge branch 'master' into merge_k_ll_improve
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‎DIRECTORY.md

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* [CircleLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/CircleLinkedListTest.java)
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* [CreateAndDetectLoopTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/CreateAndDetectLoopTest.java)
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* [MergeKSortedLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/MergeKSortedLinkedListTest.java)
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* [MergeSortedArrayListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/MergeSortedArrayListTest.java)
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* [MergeSortedSinglyLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/MergeSortedSinglyLinkedListTest.java)
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* [QuickSortLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/QuickSortLinkedListTest.java)
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* [ReverseKGroupTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/ReverseKGroupTest.java)

‎src/main/java/com/thealgorithms/datastructures/lists/MergeSortedArrayList.java

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package com.thealgorithms.datastructures.lists;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.List;
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/**
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* Utility class for merging two sorted ArrayLists of integers into a single sorted collection.
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*
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* <p>This class provides a static `merge` method to combine two pre-sorted lists of integers into a
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* single sorted list. It does so without modifying the input lists by adding elements from both lists in sorted order
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* into the result list.</p>
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*
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* <p>Example usage:</p>
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* <pre>
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* List<Integer> listA = Arrays.asList(1, 3, 5, 7, 9);
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* List<Integer> listB = Arrays.asList(2, 4, 6, 8, 10);
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* List<Integer> result = new ArrayList<>();
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* MergeSortedArrayList.merge(listA, listB, result);
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* </pre>
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*
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* <p>The resulting `result` list will be [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].</p>
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*
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* <p>Note: This class cannot be instantiated as it is designed to be used only with its static `merge` method.</p>
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*
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* <p>This implementation assumes the input lists are already sorted in ascending order.</p>
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*
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* @author https://github.com/shellhub
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* @see List
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*/
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public final class MergeSortedArrayList {
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private MergeSortedArrayList() {
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}
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public static void main(String[] args) {
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List<Integer> listA = new ArrayList<>();
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List<Integer> listB = new ArrayList<>();
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List<Integer> listC = new ArrayList<>();
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/* init ListA and List B */
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for (int i = 1; i <= 10; i += 2) {
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listA.add(i);
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/* listA: [1, 3, 5, 7, 9] */
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listB.add(i + 1);
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/* listB: [2, 4, 6, 8, 10] */
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}
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/* merge listA and listB to listC */
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merge(listA, listB, listC);
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System.out.println("listA: " + listA);
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System.out.println("listB: " + listB);
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System.out.println("listC: " + listC);
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private MergeSortedArrayList() {
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}
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/**
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* merge two sorted ArrayList
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* Merges two sorted lists of integers into a single sorted collection.
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*
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* <p>This method does not alter the original lists (`listA` and `listB`). Instead, it inserts elements from both
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* lists into `listC` in a way that maintains ascending order.</p>
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*
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* @param listA the first list to merge
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* @param listB the second list to merge
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* @param listC the result list after merging
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* @param listA The first sorted list of integers.
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* @param listB The second sorted list of integers.
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* @param listC The collection to hold the merged result, maintaining sorted order.
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* @throws NullPointerException if any of the input lists or result collection is null.
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*/
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public static void merge(List<Integer> listA, List<Integer> listB, Collection<Integer> listC) {
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if (listA == null || listB == null || listC == null) {
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throw new NullPointerException("Input lists and result collection must not be null.");
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}
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int pa = 0;
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/* the index of listA */
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int pb = 0;
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/* the index of listB */
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while (pa < listA.size() && pb < listB.size()) {
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if (listA.get(pa) <= listB.get(pb)) {
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}
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}
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/* copy left element of listA to listC */
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// Add remaining elements from listA, if any
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while (pa < listA.size()) {
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listC.add(listA.get(pa++));
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}
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/* copy left element of listB to listC */
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// Add remaining elements from listB, if any
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while (pb < listB.size()) {
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listC.add(listB.get(pb++));
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}

‎src/test/java/com/thealgorithms/datastructures/lists/MergeSortedArrayListTest.java

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package com.thealgorithms.datastructures.lists;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import org.junit.jupiter.api.Test;
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class MergeSortedArrayListTest {
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@Test
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void testMergeTwoSortedLists() {
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List<Integer> listA = Arrays.asList(1, 3, 5, 7, 9);
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List<Integer> listB = Arrays.asList(2, 4, 6, 8, 10);
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List<Integer> result = new ArrayList<>();
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MergeSortedArrayList.merge(listA, listB, result);
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List<Integer> expected = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
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assertEquals(expected, result, "Merged list should be sorted and contain all elements from both input lists.");
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}
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@Test
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void testMergeWithEmptyList() {
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List<Integer> listA = Arrays.asList(1, 2, 3);
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List<Integer> listB = new ArrayList<>(); // Empty list
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List<Integer> result = new ArrayList<>();
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MergeSortedArrayList.merge(listA, listB, result);
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List<Integer> expected = Arrays.asList(1, 2, 3);
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assertEquals(expected, result, "Merged list should match listA when listB is empty.");
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}
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@Test
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void testMergeWithBothEmptyLists() {
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List<Integer> listA = new ArrayList<>(); // Empty list
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List<Integer> listB = new ArrayList<>(); // Empty list
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List<Integer> result = new ArrayList<>();
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MergeSortedArrayList.merge(listA, listB, result);
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assertTrue(result.isEmpty(), "Merged list should be empty when both input lists are empty.");
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}
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@Test
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void testMergeWithDuplicateElements() {
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List<Integer> listA = Arrays.asList(1, 2, 2, 3);
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List<Integer> listB = Arrays.asList(2, 3, 4);
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List<Integer> result = new ArrayList<>();
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MergeSortedArrayList.merge(listA, listB, result);
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List<Integer> expected = Arrays.asList(1, 2, 2, 2, 3, 3, 4);
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assertEquals(expected, result, "Merged list should correctly handle and include duplicate elements.");
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}
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@Test
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void testMergeWithNegativeAndPositiveNumbers() {
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List<Integer> listA = Arrays.asList(-3, -1, 2);
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List<Integer> listB = Arrays.asList(-2, 0, 3);
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List<Integer> result = new ArrayList<>();
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MergeSortedArrayList.merge(listA, listB, result);
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List<Integer> expected = Arrays.asList(-3, -2, -1, 0, 2, 3);
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assertEquals(expected, result, "Merged list should correctly handle negative and positive numbers.");
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}
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@Test
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void testMergeThrowsExceptionOnNullInput() {
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List<Integer> listA = null;
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List<Integer> listB = Arrays.asList(1, 2, 3);
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List<Integer> result = new ArrayList<>();
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List<Integer> finalListB = listB;
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List<Integer> finalListA = listA;
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List<Integer> finalResult = result;
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assertThrows(NullPointerException.class, () -> MergeSortedArrayList.merge(finalListA, finalListB, finalResult), "Should throw NullPointerException if any input list is null.");
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listA = Arrays.asList(1, 2, 3);
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listB = null;
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List<Integer> finalListA1 = listA;
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List<Integer> finalListB1 = listB;
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List<Integer> finalResult1 = result;
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assertThrows(NullPointerException.class, () -> MergeSortedArrayList.merge(finalListA1, finalListB1, finalResult1), "Should throw NullPointerException if any input list is null.");
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listA = Arrays.asList(1, 2, 3);
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listB = Arrays.asList(4, 5, 6);
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result = null;
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List<Integer> finalListA2 = listA;
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List<Integer> finalListB2 = listB;
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List<Integer> finalResult2 = result;
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assertThrows(NullPointerException.class, () -> MergeSortedArrayList.merge(finalListA2, finalListB2, finalResult2), "Should throw NullPointerException if the result collection is null.");
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}
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}

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