/*******************************************************************************
* 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<T> implements Iterator<T> {
final ArrayList<T> list = new ArrayList<T>();
int nextIndex;
/**
* @param other
* the iterator to reverse
* @throws IllegalArgumentException if other == null
*/
private ReverseIterator(Iterator<T> other) throws IllegalArgumentException {
if (other == null) {
throw new IllegalArgumentException("other == null");
}
while (other.hasNext()) {
list.add(other.next());
}
nextIndex = list.size() - 1;
}
@Override
public boolean hasNext() {
return nextIndex > -1;
}
@Override
public T next() throws NoSuchElementException {
if (!hasNext()) {
throw new NoSuchElementException();
}
return list.get(nextIndex--);
}
@Override
public void remove() throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
public static <T> Iterator<T> reverse(Iterator<T> it) {
return new ReverseIterator<T>(it);
}
}