com.day.util.CompoundIterator Maven / Gradle / Ivy

/*
 * $Id: CompoundIterator.java 12345 2004-08-22 04:56:09Z fielding $
 *
 * Copyright 1997-2004 Day Management AG
 * Barfuesserplatz 6, 4001 Basel, Switzerland
 * All Rights Reserved.
 *
 * This software is the confidential and proprietary information of
 * Day Management AG, ("Confidential Information"). You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Day.
 */

package com.day.util;

import java.util.Iterator;

/**
 * Implements the Iterator interface and combines two
 * Iterator objects into one single Iterator.
 * 
 * The constructor takes two Iterator arguments: parent
 * and child. Calling {@link #next} on this Iterator
 * will first try to return an element from the parent Iterator
 * and once the parent Iterator does not have any more elements
 * it will return elements from the child Iterator.
 *
 * @version $Revision: 1.2 $, $Date: 2004-08-22 06:56:09 +0200 (Sun, 22 Aug 2004) $
 * @author mreutegg
 * @since fennec
 * @audience wad
 */
public class CompoundIterator implements Iterator {

    /**
     * The parent Iterator. Elements from this
     * Iterator are returned first.
     */
    private final Iterator parent;

    /**
     * The child Iterator. Elements from this
     * Iterator are returned, after the parent
     * Iterator does not have elements any more.
     */
    private final Iterator child;

    /**
     * Creates a CompoundIterator based on parent
     * and child. This CompountIterator will first
     * return elements from parent and then elements from
     * child.
     * @param parent the Iterator from where to return the elements
     *  first.
     * @param child the Iterator from where to return the elements
     *  after parent does not have elements any more.
     */
    public CompoundIterator(Iterator parent, Iterator child) {
	this.parent = parent;
	this.child = child;
    }

    /**
     * Returns true if either parent or child iterator
     * has a next element; false otherwise.
     * @return true if either parent or child iterator
     *  has a next element; false otherwise.
     */
    public boolean hasNext() {
	return parent.hasNext() || child.hasNext();
    }

    /**
     * Returns the next element from the parent or the child
     * iterator object.
     * @return the next element from the parent or the child
     *  iterator object.
     */
    public Object next() {
	return (parent.hasNext()) ? parent.next() : child.next();
    }

    /**
     * Always throws UnsupportedOperationException
     * @throws UnsupportedOperationException always!
     */
    public void remove() throws UnsupportedOperationException {
    	throw new UnsupportedOperationException("remove() is not supported in CompoundInterator");
    }
}