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Posted to commits@commons.apache.org by tn...@apache.org on 2013/04/18 23:06:40 UTC
svn commit: r1469577 - in /commons/proper/collections/trunk/src:
changes/changes.xml
main/java/org/apache/commons/collections4/CollectionUtils.java
test/java/org/apache/commons/collections4/CollectionUtilsTest.java
Author: tn
Date: Thu Apr 18 21:06:40 2013
New Revision: 1469577
URL: http://svn.apache.org/r1469577
Log:
[COLLECTIONS-296] Added CollectionUtils#merge methods to merge two sorted Collections. Thanks to Julius Davies for the report and patch.
Modified:
commons/proper/collections/trunk/src/changes/changes.xml
commons/proper/collections/trunk/src/main/java/org/apache/commons/collections4/CollectionUtils.java
commons/proper/collections/trunk/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java
Modified: commons/proper/collections/trunk/src/changes/changes.xml
URL: http://svn.apache.org/viewvc/commons/proper/collections/trunk/src/changes/changes.xml?rev=1469577&r1=1469576&r2=1469577&view=diff
==============================================================================
--- commons/proper/collections/trunk/src/changes/changes.xml (original)
+++ commons/proper/collections/trunk/src/changes/changes.xml Thu Apr 18 21:06:40 2013
@@ -22,6 +22,10 @@
<body>
<release version="4.0" date="TBA" description="Next release">
+ <action issue="COLLECTIONS-296" dev="tn" type="add" due-to="Julius Davies">
+ Added methods "CollectionUtils#merge(...)" to merge two sorted Collections
+ into a sorted List using the standard O(n) merge algorithm.
+ </action>
<action issue="COLLECTIONS-429,COLLECTION-434" dev="tn" type="add" due-to="Adrian Nistor, Mert Guldur">
Added method "CollectionUtils#containsAll(Collection, Collection)" with guaranteed
runtime complexity of O(n + m) and space complexity of O(n). This method may yield much
Modified: commons/proper/collections/trunk/src/main/java/org/apache/commons/collections4/CollectionUtils.java
URL: http://svn.apache.org/viewvc/commons/proper/collections/trunk/src/main/java/org/apache/commons/collections4/CollectionUtils.java?rev=1469577&r1=1469576&r2=1469577&view=diff
==============================================================================
--- commons/proper/collections/trunk/src/main/java/org/apache/commons/collections4/CollectionUtils.java (original)
+++ commons/proper/collections/trunk/src/main/java/org/apache/commons/collections4/CollectionUtils.java Thu Apr 18 21:06:40 2013
@@ -19,6 +19,7 @@ package org.apache.commons.collections4;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
+import java.util.Comparator;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
@@ -1440,6 +1441,152 @@ public class CollectionUtils {
//-----------------------------------------------------------------------
/**
+ * Merges two sorted Collections, a and b, into a single, sorted List
+ * such that the natural ordering of the elements is retained.
+ * <p>
+ * Uses the standard O(n) merge algorithm for combining two sorted lists.
+ *
+ * @param <O> the element type
+ * @param a the first collection, must not be null
+ * @param b the second collection, must not be null
+ * @return a new sorted List, containing the elements of Collection a and b
+ * @throws IllegalArgumentException if either collection is null
+ */
+ public static <O extends Comparable<? super O>> List<O> merge(Collection<? extends O> a,
+ Collection<? extends O> b) {
+ return merge(a, b, ComparatorUtils.<O>naturalComparator(), true);
+ }
+
+ /**
+ /**
+ * Merges two sorted Collections, a and b, into a single, sorted List
+ * such that the natural ordering of the elements is retained.
+ * <p>
+ * Uses the standard O(n) merge algorithm for combining two sorted lists.
+ *
+ * @param <O> the element type
+ * @param a the first collection, must not be null
+ * @param b the second collection, must not be null
+ * @param includeDuplicates if {@code true} duplicate elements will be retained, otherwise
+ * they will be removed in the output collection
+ * @return a new sorted List, containing the elements of Collection a and b
+ * @throws IllegalArgumentException if either collection is null
+ */
+ public static <O extends Comparable<? super O>> List<O> merge(final Collection<? extends O> a,
+ final Collection<? extends O> b,
+ final boolean includeDuplicates) {
+ return merge(a, b, ComparatorUtils.<O>naturalComparator(), includeDuplicates);
+ }
+
+ /**
+ * Merges two sorted Collections, a and b, into a single, sorted List
+ * such that the ordering of the elements according to Comparator c is retained.
+ * <p>
+ * Uses the standard O(n) merge algorithm for combining two sorted lists.
+ *
+ * @param <O> the element type
+ * @param a the first collection, must not be null
+ * @param b the second collection, must not be null
+ * @param c the comparator to use for the merge.
+ * @return a new sorted List, containing the elements of Collection a and b
+ * @throws IllegalArgumentException if either collection or the comparator is null
+ */
+ public static <O> List<O> merge(final Collection<? extends O> a, final Collection<? extends O> b,
+ final Comparator<? super O> c) {
+ return merge(a, b, c, true);
+ }
+
+ /**
+ * Merges two sorted Collections, a and b, into a single, sorted List
+ * such that the ordering of the elements according to Comparator c is retained.
+ * <p>
+ * Uses the standard O(n) merge algorithm for combining two sorted lists.
+ *
+ * @param <O> the element type
+ * @param a the first collection, must not be null
+ * @param b the second collection, must not be null
+ * @param c the comparator to use for the merge.
+ * @param includeDuplicates if {@code true} duplicate elements will be retained, otherwise
+ * they will be removed in the output collection
+ * @return a new sorted List, containing the elements of Collection a and b
+ * @throws IllegalArgumentException if either collection or the comparator is null
+ */
+ public static <O> List<O> merge(final Collection<? extends O> a, final Collection<? extends O> b,
+ final Comparator<? super O> c, final boolean includeDuplicates) {
+
+ if (a == null || b == null) {
+ throw new IllegalArgumentException("The collections must not be null");
+ }
+ if (c == null) {
+ throw new IllegalArgumentException("The comparator must not be null");
+ }
+
+ final List<O> mergedList = new ArrayList<O>(a.size() + b.size());
+
+ // if either collection is empty, just return the other one
+ if (a.isEmpty() || b.isEmpty()) {
+ mergedList.addAll(a.isEmpty() ? b : a);
+ return mergedList;
+ }
+
+ final Iterator<? extends O> it1 = a.iterator();
+ final Iterator<? extends O> it2 = b.iterator();
+ O o1 = it1.next();
+ O o2 = it2.next();
+ O last = null;
+ while (true) {
+ final int x = c.compare(o1, o2);
+ if (x <= 0) {
+ last = addItemToList(o1, mergedList, last, includeDuplicates);
+ if (it1.hasNext()) {
+ o1 = it1.next();
+ } else {
+ // a is empty, so add current element of b
+ last = addItemToList(o2, mergedList, last, includeDuplicates);
+ break;
+ }
+ } else {
+ last = addItemToList(o2, mergedList, last, includeDuplicates);
+ if (it2.hasNext()) {
+ o2 = it2.next();
+ } else {
+ // b is empty, so add current element of a
+ last = addItemToList(o1, mergedList, last, includeDuplicates);
+ break;
+ }
+ }
+ }
+
+ // add the remaining elements from the non-empty iterator
+ final Iterator<? extends O> it = it1.hasNext() ? it1 : it2;
+ while (it.hasNext()) {
+ last = addItemToList(it.next(), mergedList, last, includeDuplicates);
+ }
+
+ return mergedList;
+ }
+
+ /**
+ * Adds an item to the specified list.
+ *
+ * @param item the item to add
+ * @param list the list to use
+ * @param lastItem the last added item, may be null
+ * @param includeDuplicates whether duplicate entries are allowed
+ * @return the last added item
+ */
+ private static <E> E addItemToList(final E item, final List<E> list, final E lastItem,
+ final boolean includeDuplicates) {
+ if (includeDuplicates || lastItem == null || !lastItem.equals(item)) {
+ list.add(item);
+ return item;
+ } else {
+ return lastItem;
+ }
+ }
+
+ //-----------------------------------------------------------------------
+ /**
* Returns a collection containing all the elements in <code>collection</code>
* that are also in <code>retain</code>. The cardinality of an element <code>e</code>
* in the returned collection is the same as the cardinality of <code>e</code>
Modified: commons/proper/collections/trunk/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java
URL: http://svn.apache.org/viewvc/commons/proper/collections/trunk/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java?rev=1469577&r1=1469576&r2=1469577&view=diff
==============================================================================
--- commons/proper/collections/trunk/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java (original)
+++ commons/proper/collections/trunk/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java Thu Apr 18 21:06:40 2013
@@ -71,6 +71,16 @@ public class CollectionUtilsTest extends
private Collection<Integer> collectionC = null;
/**
+ * Sorted Collection of {@link Integer}s
+ */
+ private Collection<Integer> collectionD = null;
+
+ /**
+ * Sorted Collection of {@link Integer}s
+ */
+ private Collection<Integer> collectionE = null;
+
+ /**
* Collection of {@link Integer}s, bound as {@link Number}s
*/
private Collection<Number> collectionA2 = null;
@@ -96,6 +106,8 @@ public class CollectionUtilsTest extends
private Iterable<Number> iterableB2 = null;
+ private Collection<Integer> emptyCollection = new ArrayList<Integer>(1);
+
@Before
public void setUp() {
collectionA = new ArrayList<Integer>();
@@ -134,6 +146,25 @@ public class CollectionUtilsTest extends
collectionC2 = new LinkedList<Number>(collectionC);
iterableA2 = collectionA2;
iterableB2 = collectionB2;
+
+ collectionD = new ArrayList<Integer>();
+ collectionD.add(1);
+ collectionD.add(3);
+ collectionD.add(3);
+ collectionD.add(3);
+ collectionD.add(5);
+ collectionD.add(7);
+ collectionD.add(7);
+ collectionD.add(10);
+
+ collectionE = new ArrayList<Integer>();
+ collectionE.add(2);
+ collectionE.add(4);
+ collectionE.add(4);
+ collectionE.add(5);
+ collectionE.add(6);
+ collectionE.add(6);
+ collectionE.add(9);
}
@Test
@@ -1553,4 +1584,65 @@ public class CollectionUtilsTest extends
expect(iterator.hasNext()).andReturn(true);
expect(iterator.next()).andReturn(t);
}
+
+ @Test(expected=IllegalArgumentException.class)
+ public void mergeException1() {
+ CollectionUtils.merge(collectionA, null);
+ }
+
+ @Test(expected=IllegalArgumentException.class)
+ public void mergeException2() {
+ CollectionUtils.merge(collectionA, collectionC, null);
+ }
+
+ @Test
+ public void testMerge() {
+ List<Integer> result = CollectionUtils.merge(emptyCollection, emptyCollection);
+ assertEquals("Merge empty with empty", 0, result.size());
+
+ result = CollectionUtils.merge(collectionA, emptyCollection);
+ assertEquals("Merge empty with non-empty", collectionA, result);
+
+ List<Integer> result1 = CollectionUtils.merge(collectionD, collectionE);
+ List<Integer> result2 = CollectionUtils.merge(collectionE, collectionD);
+ assertEquals("Merge two lists 1", result1, result2);
+
+ List<Integer> combinedList = new ArrayList<Integer>();
+ combinedList.addAll(collectionD);
+ combinedList.addAll(collectionE);
+ Collections.sort(combinedList);
+
+ assertEquals("Merge two lists 2", combinedList, result2);
+
+ final Comparator<Integer> reverseComparator =
+ ComparatorUtils.reversedComparator(ComparatorUtils.<Integer>naturalComparator());
+
+ result = CollectionUtils.merge(emptyCollection, emptyCollection, reverseComparator);
+ assertEquals("Comparator Merge empty with empty", 0, result.size());
+
+ Collections.reverse((List<Integer>) collectionD);
+ Collections.reverse((List<Integer>) collectionE);
+ Collections.reverse(combinedList);
+
+ result1 = CollectionUtils.merge(collectionD, collectionE, reverseComparator);
+ result2 = CollectionUtils.merge(collectionE, collectionD, reverseComparator);
+ assertEquals("Comparator Merge two lists 1", result1, result2);
+ assertEquals("Comparator Merge two lists 2", combinedList, result2);
+ }
+
+ @Test
+ public void testMergeIgnoreDuplicates() {
+ List<Integer> result1 = CollectionUtils.merge(collectionD, collectionE, false);
+ List<Integer> result2 = CollectionUtils.merge(collectionE, collectionD, false);
+ assertEquals("Merge two lists 1 - ignore duplicates", result1, result2);
+
+ Set<Integer> combinedSet = new HashSet<Integer>();
+ combinedSet.addAll(collectionD);
+ combinedSet.addAll(collectionE);
+ List<Integer> combinedList = new ArrayList<Integer>(combinedSet);
+ Collections.sort(combinedList);
+
+ assertEquals("Merge two lists 2 - ignore duplicates", combinedList, result2);
+ }
+
}