A Simple Iterator for an Array of Objects

package com.darwinsys;
 
/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * Java, the Duke mascot, and all variants of Sun's Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun's, and James Gosling's,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */
 
import java.util.Iterator;
 
/**
 * De-mystify the Iterator interface, showing how to write a simple Iterator for an Array of Objects.
 * 
 * @author Ian Darwin, http://www.darwinsys.com/
 * @version $Id: ArrayIterator.java,v 1.10 2004/06/16 17:39:33 ian Exp $
 */
public class ArrayIterator implements Iterator {
    /** The data to be iterated over. */
    protected Object[] data;
 
    protected int index = 0;
 
    /**
     * Construct an ArrayIterator object.
     * 
     * @param d
     *            The array of objects to be iterated over.
     */
    public ArrayIterator(final Object[] d) {
	setData(d);
    }
 
    /**
     * (Re)set the data array to the given array, and reset the iterator.
     * 
     * @param d
     *            The array of objects to be iterated over.
     */
    public void setData(final Object[] d) {
	this.data = d;
	index = 0;
    }
 
    /**
     * Tell if there are any more elements.
     * 
     * @return true if not at the end, i.e., if next() will succeed.
     * @return false if next() will throw an exception.
     */
    public boolean hasNext() {
	return (index < data.length);
    }
 
    /** Returns the next element from the data */
    public Object next() {
	if (hasNext()) {
	    return data[index++];
	}
	throw new IndexOutOfBoundsException("only " + data.length + " elements");
    }
 
    /**
     * Remove the object that next() just returned. An Iterator is not required to support this interface, and we certainly don't!
     */
    public void remove() {
	throw new UnsupportedOperationException("This demo does not implement the remove method");
    }
}