An IteratorChain is a sequence of Iterators called until all Iterators are
exhausted git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@130686 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Morgan James Delagrange
parent
cf75b03503
commit
baf631663d
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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/Attic/IteratorChain.java,v 1.1 2002/04/08 23:38:48 morgand Exp $
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* $Revision: 1.1 $
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* $Date: 2002/04/08 23:38:48 $
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*
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* ====================================================================
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*
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* The Apache Software License, Version 1.1
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*
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* Copyright (c) 1999-2001 The Apache Software Foundation. All rights
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* reserved.
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*
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* Redistribution and use in source and binary forms, with or without
|
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* modification, are permitted provided that the following conditions
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* are met:
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*
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||||
* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
|
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. The end-user documentation included with the redistribution, if
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* any, must include the following acknowlegement:
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* "This product includes software developed by the
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* Apache Software Foundation (http://www.apache.org/)."
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* Alternately, this acknowlegement may appear in the software itself,
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* if and wherever such third-party acknowlegements normally appear.
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*
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* 4. The names "The Jakarta Project", "Commons", and "Apache Software
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* Foundation" must not be used to endorse or promote products derived
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* from this software without prior written permission. For written
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* permission, please contact apache@apache.org.
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*
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* 5. Products derived from this software may not be called "Apache"
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* nor may "Apache" appear in their names without prior written
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* permission of the Apache Group.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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* ====================================================================
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*
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* This software consists of voluntary contributions made by many
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* individuals on behalf of the Apache Software Foundation. For more
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* information on the Apache Software Foundation, please see
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* <http://www.apache.org/>.
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*
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*/
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package org.apache.commons.collections;
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import java.util.ArrayList;
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import java.util.Iterator;
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import java.util.List;
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import java.util.NoSuchElementException;
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/**
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* <p>An IteratorChain is an Iterator that wraps one or
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* more Iterators in sequence. When any method from the
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* Iterator interface is called, the IteratorChain will
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* call the same method on the first Iterator in the chain
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* until it is exhausted until the first Iterator is exhausted.
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* At that point, the IteratorChain will move to the next
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* Iterator in the IteratorChain. The IteratorChain will
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* continue in this pattern until all Iterators in the
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* IteratorChain are exhausted.</p>
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*
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* <p>Under many circumstances, linking Iterators together
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* in this manner is more efficient (and convenient)
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* than reading out the contents of each Iterator into a
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* List and creating a new Iterator.</p>
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*
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* <p>IteratorChain is Serializable, but there is no
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* guarantee that the underlying Iterators are
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* Serializable.</p>
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*
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* <p>Calling a method that adds new Iterator<i>after
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* a method in the Iterator interface
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* has been called</i> will result in an
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* UnsupportedOperationException. However, <i>take care</i>
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* to not alter the underlying List of Iterators.</p>
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*
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* @author Morgan Delagrange
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*/
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public class IteratorChain implements Iterator {
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protected List iteratorChain = null;
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protected int currentIteratorIndex = 0;
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protected Iterator currentIterator = null;
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// the "last used" Iterator is the Iterator upon which
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// next() or hasNext() was most recently called
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// used for the remove() operation only
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protected Iterator lastUsedIterator = null;
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// ComparatorChain is "locked" after the first time
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// compare(Object,Object) is called
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protected boolean isLocked = false;
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/**
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* Construct an IteratorChain with no Iterators.
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* You must add at least Iterator before calling
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* any method from the Iterator interface, or an
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* UnsupportedOperationException is thrown
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*/
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public IteratorChain() {
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this(new ArrayList());
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}
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/**
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* Construct an IteratorChain with a single Iterator.
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*
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* @param iterator first Iterator in the IteratorChain
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*/
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public IteratorChain(Iterator iterator) {
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iteratorChain = new ArrayList();
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iteratorChain.add(iterator);
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}
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/**
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* Construct an IteratorChain from the Iterators in the
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* List.
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*
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* @param list List of Iterators
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*/
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public IteratorChain(List list) {
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iteratorChain = list;
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}
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/**
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* Add an Iterator to the end of the chain
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*
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* @param iterator Iterator to add
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*/
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public void addIterator(Iterator iterator) {
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checkLocked();
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iteratorChain.add(iterator);
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}
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/**
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* Replace the Iterator at the given index
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*
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* @param index index of the Iterator to replace
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* @param iterator Iterator to place at the given index
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* @exception IndexOutOfBoundsException
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* if index < 0 or index > size()
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*/
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public void setIterator(int index, Iterator iterator)
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throws IndexOutOfBoundsException {
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checkLocked();
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iteratorChain.set(index,iterator);
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}
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/**
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* Number of Iterators in the current IteratorChain.
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*
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* @return Iterator count
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*/
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public int size() {
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return iteratorChain.size();
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}
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/**
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* Determine if modifications can still be made to the
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* IteratorChain. IteratorChains cannot be modified
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* once they have executed a method from the Iterator
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* interface.
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*
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* @return true = IteratorChain cannot be modified; false =
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* IteratorChain can still be modified.
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*/
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public boolean isLocked() {
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return isLocked;
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}
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// throw an exception if the IteratorChain is locked
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private void checkLocked() {
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if (isLocked == true) {
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throw new UnsupportedOperationException("IteratorChain cannot be changed after the first use of a method from the Iterator interface");
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}
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}
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private void checkChainIntegrity() {
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if (iteratorChain.size() == 0) {
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throw new UnsupportedOperationException("IteratorChains must contain at least one Iterator");
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}
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}
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// you MUST call this method whenever you call a method in the Iterator interface, because
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// this method also assigns the initial value of the currentIterator variable
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private void lockChain() {
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if (isLocked == false) {
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checkChainIntegrity();
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isLocked = true;
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}
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}
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// call this before any Iterator method to make sure that the current Iterator
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// is not exhausted
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protected void updateCurrentIterator() {
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if (currentIterator == null) {
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currentIterator = (Iterator) iteratorChain.get(0);
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// set last used iterator here, in case the user calls remove
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// before calling hasNext() or next() (although they shouldn't)
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lastUsedIterator = currentIterator;
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return;
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}
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if (currentIteratorIndex == (iteratorChain.size() - 1)) {
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return;
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}
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while (currentIterator.hasNext() == false) {
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++currentIteratorIndex;
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currentIterator = (Iterator) iteratorChain.get(currentIteratorIndex);
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if (currentIteratorIndex == (iteratorChain.size() - 1)) {
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return;
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}
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}
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}
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/**
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* Return true if any Iterator in the IteratorChain has a remaining
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* element.
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*
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* @return true if elements remain
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* @exception UnsupportedOperationException
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* if the IteratorChain does not contain at least one
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* Iterator
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*/
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public boolean hasNext() throws UnsupportedOperationException {
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lockChain();
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updateCurrentIterator();
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lastUsedIterator = currentIterator;
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return currentIterator.hasNext();
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}
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/**
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* Returns the next Object of the current Iterator
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*
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* @return Object from the current Iterator
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* @exception NoSuchElementException
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* if all the Iterators are exhausted
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* @exception UnsupportedOperationException
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* if the IteratorChain does not contain at least one
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* Iterator
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*/
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public Object next() throws NoSuchElementException, UnsupportedOperationException {
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lockChain();
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updateCurrentIterator();
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lastUsedIterator = currentIterator;
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return currentIterator.next();
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}
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/**
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* Removes from the underlying collection the last element
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* returned by the Iterator. As with next() and hasNext(),
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* this method calls remove() on the underlying Iterator.
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* Therefore, this method may throw an
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* UnsupportedOperationException if the underlying
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* Iterator does not support this method.
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*
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* @exception UnsupportedOperationException
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* if the remove operator is not supported by the underlying
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* Iterator or if there are no Iterators in the IteratorChain
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* @exception IllegalStateException
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* if the next method has not yet been called, or the
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* remove method has already been called after the last
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* call to the next method.
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*/
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public void remove() throws UnsupportedOperationException, IllegalStateException {
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lockChain();
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updateCurrentIterator();
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lastUsedIterator.remove();
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}
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}
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@ -0,0 +1,180 @@
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/*
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* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/test/org/apache/commons/collections/Attic/TestIteratorChain.java,v 1.1 2002/04/08 23:39:01 morgand Exp $
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* $Revision: 1.1 $
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* $Date: 2002/04/08 23:39:01 $
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*
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* ====================================================================
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*
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* The Apache Software License, Version 1.1
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*
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* Copyright (c) 1999-2001 The Apache Software Foundation. All rights
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* reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
|
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
|
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. The end-user documentation included with the redistribution, if
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* any, must include the following acknowlegement:
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* "This product includes software developed by the
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* Apache Software Foundation (http://www.apache.org/)."
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* Alternately, this acknowlegement may appear in the software itself,
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* if and wherever such third-party acknowlegements normally appear.
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*
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* 4. The names "The Jakarta Project", "Commons", and "Apache Software
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* Foundation" must not be used to endorse or promote products derived
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* from this software without prior written permission. For written
|
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* permission, please contact apache@apache.org.
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*
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* 5. Products derived from this software may not be called "Apache"
|
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* nor may "Apache" appear in their names without prior written
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* permission of the Apache Group.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
|
||||
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
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* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
|
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
||||
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
|
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
|
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
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* SUCH DAMAGE.
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||||
* ====================================================================
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*
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* This software consists of voluntary contributions made by many
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* individuals on behalf of the Apache Software Foundation. For more
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* information on the Apache Software Foundation, please see
|
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* <http://www.apache.org/>.
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*
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*/
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package org.apache.commons.collections;
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import junit.framework.*;
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import java.io.Serializable;
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import java.util.ArrayList;
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import java.util.Iterator;
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import java.util.List;
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import java.util.NoSuchElementException;
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/**
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* Tests the ArrayIterator to ensure that the next() method will actually
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* perform the iteration rather than the hasNext() method.
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* The code of this test was supplied by Mauricio S. Moura
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*
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* @author James Strachan
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* @author Mauricio S. Moura
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* @author Morgan Delagrange
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* @version $Id: TestIteratorChain.java,v 1.1 2002/04/08 23:39:01 morgand Exp $
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*/
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public class TestIteratorChain extends TestIterator {
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protected String[] testArray = {
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"One", "Two", "Three", "Four", "Five", "Six"
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};
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protected List list1 = null;
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protected List list2 = null;
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protected List list3 = null;
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public static Test suite() {
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return new TestSuite(TestIteratorChain.class);
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}
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public TestIteratorChain(String testName) {
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super(testName);
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}
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public void setUp() {
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list1 = new ArrayList();
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list1.add("One");
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list1.add("Two");
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list1.add("Three");
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list2 = new ArrayList();
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list2.add("Four");
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list3 = new ArrayList();
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list3.add("Five");
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list3.add("Six");
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}
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public Iterator makeEmptyIterator() {
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ArrayList list = new ArrayList();
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return new IteratorChain(list.iterator());
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}
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public Iterator makeFullIterator() {
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IteratorChain chain = new IteratorChain();
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Iterator i = list1.iterator();
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chain.addIterator(list1.iterator());
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chain.addIterator(list2.iterator());
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chain.addIterator(list3.iterator());
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return chain;
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}
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/**
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* Return a new, empty {@link Object} to used for testing.
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*/
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public Object makeObject() {
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return makeFullIterator();
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}
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public void testIterator() {
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Iterator iter = (Iterator) makeFullIterator();
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for ( int i = 0; i < testArray.length; i++ ) {
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Object testValue = testArray[i];
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Object iterValue = iter.next();
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assertEquals( "Iteration value is correct", testValue, iterValue );
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}
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assertTrue("Iterator should now be empty", ! iter.hasNext() );
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try {
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Object testValue = iter.next();
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} catch (Exception e) {
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assertTrue("NoSuchElementException must be thrown",
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e.getClass().equals((new NoSuchElementException()).getClass()));
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}
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}
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public void testRemove() {
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Iterator iter = (Iterator) makeFullIterator();
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try {
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iter.remove();
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fail("Calling remove before the first call to next() should throw an exception");
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} catch (IllegalStateException e) {
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}
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for ( int i = 0; i < testArray.length; i++ ) {
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Object testValue = testArray[i];
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Object iterValue = iter.next();
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assertEquals( "Iteration value is correct", testValue, iterValue );
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if (! iterValue.equals("Four")) {
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iter.remove();
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}
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}
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assertTrue("List is empty",list1.size() == 0);
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assertTrue("List is empty",list2.size() == 1);
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assertTrue("List is empty",list3.size() == 0);
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}
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||||
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}
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