Add filter() and transform()
Add lots of javadoc Deprecate empty iterator git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@130796 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne
parent
844eb0adcc
commit
41be9cbfa9
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@ -1,7 +1,7 @@
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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 1.13 2002/08/17 21:10:46 pjack Exp $
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* $Revision: 1.13 $
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* $Date: 2002/08/17 21:10:46 $
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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 1.14 2002/08/18 15:26:20 scolebourne Exp $
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* $Revision: 1.14 $
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* $Date: 2002/08/18 15:26:20 $
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*
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* ====================================================================
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*
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@ -68,6 +68,7 @@ import java.util.HashMap;
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import java.util.HashSet;
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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 java.util.Map;
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import java.util.NoSuchElementException;
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import java.util.Set;
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@ -78,39 +79,22 @@ import org.apache.commons.collections.iterators.EnumerationIterator;
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/**
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* A set of {@link Collection} related utility methods.
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*
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* @author Rodney Waldhoff
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*
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* @since 1.0
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* @version $Id: CollectionUtils.java,v 1.13 2002/08/17 21:10:46 pjack Exp $
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* @author Rodney Waldhoff
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* @author Paul Jack
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* @author <a href="mailto:scolebourne@joda.org">Stephen Colebourne</a>
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* @version $Id: CollectionUtils.java,v 1.14 2002/08/18 15:26:20 scolebourne Exp $
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*/
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public class CollectionUtils {
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/**
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* The empty iterator (immutable).
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* @deprecated use IteratorUtils.EMPTY_ITERATOR
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*/
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public static final Iterator EMPTY_ITERATOR = new EmptyIterator();
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public static final Iterator EMPTY_ITERATOR = IteratorUtils.EMPTY_ITERATOR;
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/**
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* 'Hidden' class which acts as an EmptyIterator.
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* An alternative is to use: Collections.EMPTY_LIST.iterator();
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* however that will create a new iterator object each time.
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*/
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private static class EmptyIterator implements Iterator {
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public boolean hasNext() {
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return false;
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}
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public Object next() {
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throw new NoSuchElementException();
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}
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public void remove() {
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throw new UnsupportedOperationException();
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}
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}
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/**
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* Please don't ever instantiate a <Code>CollectionUtils</Code>.
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* Please don't ever instantiate a <code>CollectionUtils</code>.
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*/
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public CollectionUtils() {
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}
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@ -320,18 +304,20 @@ public class CollectionUtils {
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return count;
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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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*
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* @return the first element of the collection which matches the predicate or null if none could be found
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*/
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public static Object find( Collection collection, Predicate predicate ) {
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if ( collection != null && predicate != null ) {
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for ( Iterator iter = collection.iterator(); iter.hasNext(); ) {
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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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*
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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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* @return the first element of the collection which matches the predicate or null if none could be found
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*/
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public static Object find(Collection collection, Predicate predicate) {
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if (collection != null && predicate != null) {
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for (Iterator iter = collection.iterator(); iter.hasNext();) {
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Object item = iter.next();
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if ( predicate.evaluate( item ) ) {
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if (predicate.evaluate(item)) {
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return item;
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}
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}
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@ -339,121 +325,266 @@ public class CollectionUtils {
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return null;
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}
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/** Executes the given closure on each element in the colleciton
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*/
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public static void forAllDo( Collection collection, Closure closure) {
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if ( collection != null ) {
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for ( Iterator iter = collection.iterator(); iter.hasNext(); ) {
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/**
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* Executes the given closure on each element in the collection.
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* <p>
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* If the input collection is null, there is no change made.
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*
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* @param collection the collection to get the input from, may be null
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* @param closure the closure to perform, may not be null
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* @throws NullPointerException if the closure is null
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*/
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public static void forAllDo(Collection collection, Closure closure) {
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if (collection != null) {
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for (Iterator iter = collection.iterator(); iter.hasNext();) {
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Object element = iter.next();
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closure.execute( element );
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closure.execute(element);
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}
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}
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}
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/** Selects all elements from inputCollection which match the given predicate
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* into an output collection
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*/
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public static Collection select( Collection inputCollection, Predicate predicate ) {
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ArrayList answer = new ArrayList( inputCollection.size() );
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select( inputCollection, predicate, answer );
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/**
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* Filter the collection by applying a Predicate to each element. If the
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* predicate returns false, remove the element.
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* <p>
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* If the input collection or predicate is null, there is no change made.
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*
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* @param collection the collection to get the input from, may be null
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* @param predicate the predicate to use as a filter, may be null
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*/
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public static void filter(Collection collection, Predicate predicate) {
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if (collection != null && predicate != null) {
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for (Iterator iter = collection.iterator(); iter.hasNext();) {
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Object element = iter.next();
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if (predicate.evaluate(element) == false) {
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iter.remove();
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}
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}
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}
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}
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/**
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* Transform the collection by applying a Transformer to each element.
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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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* <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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* collection may reduce in size due to calling this method.
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*
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* @param collection the collection to get the input from, may be null
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* @param transformer the transformer to perform, may be null
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*/
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public static void transform(Collection collection, Transformer transformer) {
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if (collection != null && transformer != null) {
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if (collection instanceof List) {
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List list = (List) collection;
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for (ListIterator iter = list.listIterator(); iter.hasNext();) {
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Object element = iter.next();
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iter.set(transformer.transform(element));
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}
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} else {
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Collection resultCollection = collect(collection, transformer);
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collection.clear();
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collection.addAll(resultCollection);
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}
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}
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}
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/**
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* Selects all elements from input collection which match the given predicate
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* into an output collection.
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*
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* @param inputCollection the collection to get the input from, may not be null
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* @param predicate the predicate to use, may be null
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* @return the elements matching the predicate (new list)
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* @throws NullPointerException if the input collection is null
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*/
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public static Collection select(Collection inputCollection, Predicate predicate) {
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ArrayList answer = new ArrayList(inputCollection.size());
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select(inputCollection, predicate, answer);
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return answer;
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}
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/** Selects all elements from inputCollection which match the given predicate
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* and adds them to outputCollection
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*/
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public static void select( Collection inputCollection, Predicate predicate, Collection outputCollection ) {
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if ( inputCollection != null && predicate != null ) {
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for ( Iterator iter = inputCollection.iterator(); iter.hasNext(); ) {
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/**
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* Selects all elements from input collection which match the given predicate
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* and adds them to outputCollection.
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* <p>
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* If the input collection or predicate is null, there is no change to the
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* output collection.
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*
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* @param inputCollection the collection to get the input from, may be null
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* @param predicate the predicate to use, may be null
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* @param outputCollection the collection to output into, may not be null
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* @return the outputCollection with the the elements matching the predicate added
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* @throws NullPointerException if the input collection is null
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*/
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public static void select(Collection inputCollection, Predicate predicate, Collection outputCollection) {
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if (inputCollection != null && predicate != null) {
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for (Iterator iter = inputCollection.iterator(); iter.hasNext();) {
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Object item = iter.next();
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if ( predicate.evaluate( item ) ) {
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outputCollection.add( item );
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if (predicate.evaluate(item)) {
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outputCollection.add(item);
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}
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}
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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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*/
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public static Collection collect( Collection inputCollection, Transformer transformer ) {
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ArrayList answer = new ArrayList( inputCollection.size() );
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collect( inputCollection, transformer, answer );
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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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* <p>
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* If the input transfomer is null, the result is an empty list.
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*
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* @param inputCollection the collection to get the input from, may not be null
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* @param transformer the transformer to use, may be null
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* @return the transformed result (new list)
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* @throws NullPointerException if the input collection is null
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*/
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public static Collection collect(Collection inputCollection, Transformer transformer) {
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ArrayList answer = new ArrayList(inputCollection.size());
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collect(inputCollection, transformer, answer);
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return answer;
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}
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/** Transforms all elements from the inputIterator with the given transformer
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* and adds them to the outputCollection
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*/
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public static Collection collect( Iterator inputIterator, Transformer transformer ) {
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/**
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* Transforms all elements from the inputIterator with the given transformer
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* and adds them to the outputCollection.
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* <p>
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* If the input iterator or transfomer is null, the result is an empty list.
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*
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* @param inputIterator the iterator to get the input from, may be null
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* @param transformer the transformer to use, may be null
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* @return the transformed result (new list)
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*/
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public static Collection collect(Iterator inputIterator, Transformer transformer) {
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ArrayList answer = new ArrayList();
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collect( inputIterator, transformer, answer );
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collect(inputIterator, transformer, answer);
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return answer;
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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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*
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* @return the outputCollection
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*/
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public static Collection collect( Collection inputCollection, final Transformer transformer, final Collection outputCollection ) {
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if ( inputCollection != null ) {
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return collect( inputCollection.iterator(), transformer, outputCollection );
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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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* <p>
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* If the input collection or transfomer is null, there is no change to the
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* output collection.
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*
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* @param inputCollection the collection to get the input from, may be null
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* @param transformer the transformer to use, may be null
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* @param outputCollection the collection to output into, may not be null
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* @return the outputCollection with the transformed input added
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* @throws NullPointerException if the output collection is null
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*/
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public static Collection collect(Collection inputCollection, final Transformer transformer, final Collection outputCollection) {
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if (inputCollection != null) {
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return collect(inputCollection.iterator(), transformer, outputCollection);
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}
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return outputCollection;
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}
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/** Transforms all elements from the inputIterator with the given transformer
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* and adds them to the outputCollection
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*
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* @return the outputCollection
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*/
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public static Collection collect( Iterator inputIterator, final Transformer transformer, final Collection outputCollection ) {
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if ( inputIterator != null && transformer != null ) {
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while ( inputIterator.hasNext() ) {
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/**
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* Transforms all elements from the inputIterator with the given transformer
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* and adds them to the outputCollection.
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* <p>
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* If the input iterator or transfomer is null, there is no change to the
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* output collection.
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*
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* @param inputIterator the iterator to get the input from, may be null
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* @param transformer the transformer to use, may be null
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* @param outputCollection the collection to output into, may not be null
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* @return the outputCollection with the transformed input added
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* @throws NullPointerException if the output collection is null
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*/
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public static Collection collect(Iterator inputIterator, final Transformer transformer, final Collection outputCollection) {
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if (inputIterator != null && transformer != null) {
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while (inputIterator.hasNext()) {
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Object item = inputIterator.next();
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Object value = transformer.transform( item );
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outputCollection.add( value );
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Object value = transformer.transform(item);
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outputCollection.add(value);
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}
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}
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return outputCollection;
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}
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/** Adds all elements in the iteration to the given collection
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*/
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public static void addAll( Collection collection, Iterator iterator ) {
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while ( iterator.hasNext() ) {
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collection.add( iterator.next() );
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/**
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* Adds all elements in the iteration to the given collection.
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*
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* @param collection the collection to add to
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* @param iterator the iterator of elements to add, may not be null
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* @throws NullPointerException if the collection or iterator is null
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*/
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public static void addAll(Collection collection, Iterator iterator) {
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while (iterator.hasNext()) {
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collection.add(iterator.next());
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}
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}
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/** Adds all elements in the enumeration to the given collection
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*/
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public static void addAll( Collection collection, Enumeration enumeration ) {
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while ( enumeration.hasMoreElements() ) {
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collection.add( enumeration.nextElement() );
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/**
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* Adds all elements in the enumeration to the given collection.
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*
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* @param collection the collection to add to
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* @param enumeration the enumeration of elements to add, may not be null
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* @throws NullPointerException if the collection or enumeration is null
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*/
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public static void addAll(Collection collection, Enumeration enumeration) {
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while (enumeration.hasMoreElements()) {
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collection.add(enumeration.nextElement());
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}
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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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public static void addAll( Collection collection, Object[] elements ) {
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for ( int i = 0, size = elements.length; i < size; i++ ) {
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collection.add( elements[i] );
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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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* @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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for (int i = 0, size = elements.length; i < size; i++) {
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collection.add(elements[i]);
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}
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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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* 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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* </ul>
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*
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* @param obj the object to get an index of
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* @param index the index to get
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* @throws IndexOutOfBoundsException
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* @throws NoSuchElementException
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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 an index, it will get the nth value in the
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* object.
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* Given an Object, and a key (index), it will get 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>Return the original obj.
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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 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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*/
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public static Object index(Object obj, Object index) {
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if(obj instanceof Map) {
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