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