61 lines
1.7 KiB
Java
61 lines
1.7 KiB
Java
/*******************************************************************************
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* Copyright (c) 2002 - 2006 IBM Corporation.
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* All rights reserved. This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License v1.0
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* which accompanies this distribution, and is available at
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* http://www.eclipse.org/legal/epl-v10.html
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*
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* Contributors:
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* IBM Corporation - initial API and implementation
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*******************************************************************************/
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package com.ibm.wala.util.collections;
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import java.util.ArrayList;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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/**
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* An iterator that reverses an input iterator. Not very efficient.
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*/
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public class ReverseIterator<T> implements Iterator<T> {
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final ArrayList<T> list = new ArrayList<T>();
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int nextIndex;
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/**
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* @param other
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* the iterator to reverse
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* @throws IllegalArgumentException if other == null
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*/
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private ReverseIterator(Iterator<T> other) throws IllegalArgumentException {
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if (other == null) {
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throw new IllegalArgumentException("other == null");
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}
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while (other.hasNext()) {
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list.add(other.next());
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}
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nextIndex = list.size() - 1;
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}
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public boolean hasNext() {
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return nextIndex > -1;
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}
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public T next() throws NoSuchElementException {
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if (!hasNext()) {
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throw new NoSuchElementException();
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}
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return list.get(nextIndex--);
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}
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public void remove() throws UnsupportedOperationException {
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throw new UnsupportedOperationException();
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}
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public static <T> Iterator<T> reverse(Iterator<T> it) {
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return new ReverseIterator<T>(it);
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}
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}
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