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git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@131183 13f79535-47bb-0310-9956-ffa450edef68
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Phil Steitz
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/*
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/CollectionUtils.java,v 1.42 2003/09/21 16:26:08 scolebourne Exp $
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/CollectionUtils.java,v 1.43 2003/09/21 23:47:09 psteitz Exp $
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* ====================================================================
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*
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* The Apache Software License, Version 1.1
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@ -84,7 +84,7 @@ import org.apache.commons.collections.observed.ObservableCollection;
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* Provides utility methods and decorators for {@link Collection} instances.
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*
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* @since Commons Collections 1.0
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* @version $Revision: 1.42 $ $Date: 2003/09/21 16:26:08 $
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* @version $Revision: 1.43 $ $Date: 2003/09/21 23:47:09 $
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*
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* @author Rodney Waldhoff
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* @author Paul Jack
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@ -94,6 +94,7 @@ import org.apache.commons.collections.observed.ObservableCollection;
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* @author Peter KoBek
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* @author Matthew Hawthorne
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* @author Janek Bogucki
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* @author Phil Steitz
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*/
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public class CollectionUtils {
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@ -122,6 +123,9 @@ public class CollectionUtils {
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* will be equal to the maximum of the cardinality of that element
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* in the two given {@link Collection}s.
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*
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* @param a the first collection, must not be null
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* @param b the second collection, must not be null
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* @return the union of the two collections
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* @see Collection#addAll
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*/
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public static Collection union(final Collection a, final Collection b) {
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@ -148,6 +152,9 @@ public class CollectionUtils {
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* will be equal to the minimum of the cardinality of that element
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* in the two given {@link Collection}s.
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*
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* @param a the first collection, must not be null
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* @param b the second collection, must not be null
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* @return the intersection of the two collections
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* @see Collection#retainAll
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* @see #containsAny
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*/
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@ -179,6 +186,10 @@ public class CollectionUtils {
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* <tt>{@link #subtract subtract}({@link #union union(a,b)},{@link #intersection intersection(a,b)})</tt>
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* or
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* <tt>{@link #union union}({@link #subtract subtract(a,b)},{@link #subtract subtract(b,a)})</tt>.
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*
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* @param a the first collection, must not be null
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* @param b the second collection, must not be null
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* @return the symmetric difference of the two collections
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*/
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public static Collection disjunction(final Collection a, final Collection b) {
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ArrayList list = new ArrayList();
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@ -252,7 +263,7 @@ public class CollectionUtils {
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* Only those elements present in the collection will appear as
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* keys in the map.
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*
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* @param coll the collection to get the cardinality map for
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* @param coll the collection to get the cardinality map for, must not be null
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* @return the populated cardinality map
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*/
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public static Map getCardinalityMap(final Collection coll) {
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@ -275,6 +286,9 @@ public class CollectionUtils {
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* than or equal to the cardinality of <i>e</i> in <i>b</i>,
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* for each element <i>e</i> in <i>a</i>.
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*
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* @param a the first (sub?) collection, must not be null
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* @param b the second (super?) collection, must not be null
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* @return <code>true</code> iff <i>a</i> is a sub-collection of <i>b</i>
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* @see #isProperSubCollection
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* @see Collection#containsAll
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*/
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@ -306,6 +320,9 @@ public class CollectionUtils {
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* <li><code>a.size() < Integer.MAXVALUE</code></li>
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* </ul>
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*
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* @param a the first (sub?) collection, must not be null
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* @param b the second (super?) collection, must not be null
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* @return <code>true</code> iff <i>a</i> is a <i>proper</i> sub-collection of <i>b</i>
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* @see #isSubCollection
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* @see Collection#containsAll
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*/
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@ -315,11 +332,15 @@ public class CollectionUtils {
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/**
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* Returns <tt>true</tt> iff the given {@link Collection}s contain
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* exactly the same elements with exactly the same cardinality.
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* exactly the same elements with exactly the same cardinalities.
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* <p>
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* That is, iff the cardinality of <i>e</i> in <i>a</i> is
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* equal to the cardinality of <i>e</i> in <i>b</i>,
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* for each element <i>e</i> in <i>a</i> or <i>b</i>.
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*
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* @param a the first collection, must not be null
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* @param b the second collection, must not be null
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* @return <code>true</code> iff the collections contain the same elements with the same cardinalities.
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*/
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public static boolean isEqualCollection(final Collection a, final Collection b) {
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if(a.size() != b.size()) {
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@ -345,6 +366,10 @@ public class CollectionUtils {
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/**
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* Returns the number of occurrences of <i>obj</i>
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* in <i>col</i>.
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*
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* @param obj the object to find the cardinality of
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* @param col the collection to search
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* @return the the number of occurrences of obj in col
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*/
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public static int cardinality(Object obj, final Collection col) {
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int count = 0;
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@ -367,7 +392,8 @@ public class CollectionUtils {
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/**
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* Finds the first element in the given collection which matches the given predicate.
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* <p>
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* If the input collection or predicate is null, null is returned.
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* If the input collection or predicate is null, or no element of the collection
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* matches the predicate, null is returned.
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*
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* @param collection the collection to search, may be null
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* @param predicate the predicate to use, may be null
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@ -425,8 +451,9 @@ public class CollectionUtils {
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* <p>
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* If the input collection or transformer is null, there is no change made.
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* <p>
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* This routine is best for Lists and uses set(), however it adapts for all
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* Collections that support clear() and addAll().
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* This routine is best for Lists, for which set() is used to do the
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* transformations "in place." For other Collections, clear() and addAll()
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* are used to replace elements.
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* <p>
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* If the input collection controls its input, such as a Set, and the
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* Transformer creates duplicates (or are otherwise invalid), the
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@ -569,8 +596,8 @@ public class CollectionUtils {
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}
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/**
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* Transforms all elements from inputCollection with the given transformer
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* and adds them to the outputCollection.
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* Returns a new Collection consisting of the elements of inputCollection transformed
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* by the given transformer.
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* <p>
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* If the input transformer is null, the result is an empty list.
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*
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@ -674,8 +701,8 @@ public class CollectionUtils {
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/**
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* Adds all elements in the array to the given collection.
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*
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* @param collection the collection to add to
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* @param elements the array of elements to add, may be null
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* @param collection the collection to add to, may not be null
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* @param elements the array of elements to add, may not be null
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* @throws NullPointerException if the collection or array is null
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*/
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public static void addAll(Collection collection, Object[] elements) {
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@ -685,33 +712,41 @@ public class CollectionUtils {
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}
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/**
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* Given an Object, and an index, it will get the nth value in the
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* Given an Object, and an index, returns the nth value in the
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* object.
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* <ul>
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* <li>If obj is a Map, get the nth value from the <b>key</b> iterator.
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* <li>If obj is a List or an array, get the nth value.
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* <li>If obj is an iterator, enumeration or Collection, get the nth value from the iterator.
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* <li>Return the original obj.
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* <li>If obj is a Map, returns the nth value from the <b>keySet</b> iterator, unless
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* the Map contains an Integer key with integer value = idx, in which case the
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* corresponding map entry value is returned. If idx exceeds the number of entries in
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* the map, an empty Iterator is returned.
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* <li>If obj is a List or an array, returns the nth value, throwing IndexOutOfBoundsException,
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* ArrayIndexOutOfBoundsException, resp. if the nth value does not exist.
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* <li>If obj is an iterator, enumeration or Collection, returns the nth value from the iterator,
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* returning an empty Iterator (resp. Enumeration) if the nth value does not exist.
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* <li>Returns the original obj if it is null or not a Collection or Iterator.
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* </ul>
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*
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* @param obj the object to get an index of
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* @param obj the object to get an index of, may be null
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* @param idx the index to get
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* @throws IndexOutOfBoundsException
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* @throws NoSuchElementException
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* @throws ArrayIndexOutOfBoundsException
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*/
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public static Object index(Object obj, int idx) {
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return index(obj, new Integer(idx));
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}
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/**
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* Given an Object, and a key (index), it will get value associated with
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* Given an Object, and a key (index), returns the value associated with
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* that key in the Object. The following checks are made:
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* <ul>
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* <li>If obj is a Map, use the index as a key to get a value. If no match continue.
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* <li>Check key is an Integer. If not, return the object passed in.
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* <li>If obj is a Map, get the nth value from the <b>key</b> iterator.
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* <li>If obj is a List or an array, get the nth value.
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* <li>If obj is an iterator, enumeration or Collection, get the nth value from the iterator.
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* <li>If obj is a Map, get the nth value from the <b>keySet</b> iterator.
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* If the Map has fewer than n entries, return an empty Iterator.
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* <li>If obj is a List or an array, get the nth value, throwing IndexOutOfBoundsException,
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* ArrayIndexOutOfBoundsException, resp. if the nth value does not exist.
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* <li>If obj is an iterator, enumeration or Collection, get the nth value from the iterator,
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* returning an empty Iterator (resp. Enumeration) if the nth value does not exist.
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* <li>Return the original obj.
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* </ul>
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*
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@ -719,7 +754,7 @@ public class CollectionUtils {
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* @param index the index to get
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* @return the object at the specified index
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* @throws IndexOutOfBoundsException
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* @throws NoSuchElementException
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* @throws ArrayIndexOutOfBoundsException
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*/
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public static Object index(Object obj, Object index) {
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if(obj instanceof Map) {
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