bundles/org.eclipse.core.databinding/src/org/eclipse/core/internal/databinding/RandomAccessListIterator.java

/*******************************************************************************
 * Copyright (c) 2006 The Pampered Chef and others.
 * 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:
 *     The Pampered Chef - initial API and implementation
 ******************************************************************************/

package org.eclipse.core.internal.databinding;

import java.util.List;
import java.util.ListIterator;

/**
 * Class RandomAccessListIterator.  A ListIterator implementation that also
 * provides access to individual elements based on the element's index.
 * 
 * @since 3.3
 */
public class RandomAccessListIterator implements ListIterator {
	private ListIterator delegate = null;

	/**
	 * @param iterator
	 */
	public RandomAccessListIterator(ListIterator iterator) {
		this.delegate = iterator;
	}

	/**
	 * @param list 
	 */
	public RandomAccessListIterator(List list) {
		if (list == null) {
			throw new IllegalArgumentException("list is null"); //$NON-NLS-1$
		}
		this.delegate = list.listIterator();
	}

	/* (non-Javadoc)
	 * @see java.util.ListIterator#add(java.lang.Object)
	 */
	public void add(Object arg0) {
		delegate.add(arg0);
	}

	/* (non-Javadoc)
	 * @see java.util.ListIterator#hasNext()
	 */
	public boolean hasNext() {
		return delegate.hasNext();
	}

	/* (non-Javadoc)
	 * @see java.util.ListIterator#hasPrevious()
	 */
	public boolean hasPrevious() {
		return delegate.hasPrevious();
	}

	/* (non-Javadoc)
	 * @see java.util.ListIterator#next()
	 */
	public Object next() {
		return delegate.next();
	}

	/* (non-Javadoc)
	 * @see java.util.ListIterator#nextIndex()
	 */
	public int nextIndex() {
		return delegate.nextIndex();
	}

	/* (non-Javadoc)
	 * @see java.util.ListIterator#previous()
	 */
	public Object previous() {
		return delegate.previous();
	}

	/* (non-Javadoc)
	 * @see java.util.ListIterator#previousIndex()
	 */
	public int previousIndex() {
		return delegate.previousIndex();
	}

	/* (non-Javadoc)
	 * @see java.util.ListIterator#remove()
	 */
	public void remove() {
		delegate.remove();
	}

	/* (non-Javadoc)
	 * @see java.util.ListIterator#set(java.lang.Object)
	 */
	public void set(Object arg0) {
		delegate.set(arg0);
	}
	
	/**
	 * Return the element at the specified position by moving the iterator
	 * forward or backward in the list until it reaches the correct element.
	 * The iterator's position after returning the element will be one after
	 * the element returned.
	 * 
	 * @param index The (0-based) index of the element to return.
	 * @return the Object at index
	 */
	public Object get(int index) {
		if (delegate.nextIndex() == 0 && !delegate.hasNext()) {
			throw new IndexOutOfBoundsException("Request for element from empty list"); //$NON-NLS-1$
		}
		if (index < 0) {
			throw new IndexOutOfBoundsException("Request for negative element index"); //$NON-NLS-1$
		}
		
		while (nextIndex() < index && hasNext()) {
			next();
		}
		while (previousIndex() > index-1) {
			previous();
		}
		if (!hasNext()) {
			throw new IndexOutOfBoundsException("Request for element past end of list"); //$NON-NLS-1$
		}
		return next();
	}

}