forumthreaditerator.java

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/**
 * $RCSfile: ForumThreadIterator.java,v $
 * $Revision: 1.2 $
 * $Date: 2002/05/10 22:16:57 $
 *
 * Copyright (C) 1999-2001 CoolServlets, Inc. All rights reserved.
 *
 * This software is the proprietary information of CoolServlets, Inc.
 * Use is subject to license terms.
 */

package com.jivesoftware.forum;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * An iterator for ForumThreads that allows backwards and forwards iteration,
 * as well as setting an index into the Iteration.
 */
public abstract class ForumThreadIterator implements Iterator {

    /**
     * Returns <tt>true</tt> if this iterator has more threads when
     * traversing the list in the forward direction. (In other words, returns
     * <tt>true</tt> if <tt>next</tt> would return a thread rather than
     * throwing an exception.)
     *
     * @return <tt>true</tt> if the iterator has more threads when
     *		traversing the list in the forward direction.
     */
    public abstract boolean hasNext();

    /**
     * Returns the next thread in the list. This method may be called
     * repeatedly to iterate through the list, or intermixed with calls to
     * <tt>previous</tt> to go back and forth.  (Note that alternating calls
     * to <tt>next</tt> and <tt>previous</tt> will return the same element
     * repeatedly.)
     *
     * @return the next thread in the list.
     * @exception NoSuchElementException if the iteration has no next element.
     */
    public abstract Object next();

    /**
     * Returns <tt>true</tt> if this list iterator has more threads when
     * traversing the list in the reverse direction.  (In other words, returns
     * <tt>true</tt> if <tt>previous</tt> would return a thread rather than
     * throwing an exception.)
     *
     * @return <tt>true</tt> if the list iterator has more elements when
     *	       traversing the list in the reverse direction.
     */
    public abstract boolean hasPrevious();

    /**
     * Returns the previous element in the list.  This method may be called
     * repeatedly to iterate through the list backwards, or intermixed with
     * calls to <tt>next</tt> to go back and forth.  (Note that alternating
     * calls to <tt>next</tt> and <tt>previous</tt> will return the same
     * element repeatedly.)
     *
     * @return the previous element in the list.
     *
     * @exception NoSuchElementException if the iteration has no previous
     *            element.
     */
    public abstract Object previous();

    /**
     * Sets the index for the iteration to the specified ForumThread.<p>
     *
     * Implementation note: a performance setting allows an optional short-term
     * cache so that object invalidations are delayed for a period of time. This
     * can mean that trying to set the index for a newly created thread can fail.
     * Ensure that this performance setting is disabled, or refrain from calling
     * this method with newly created threads.
     *
     * @exception NoSuchElementException if <tt>thread</tt> is not a valid
     *      element of the iteration.
     */
    public abstract void setIndex(ForumThread thread);

    /**
     * This method of the Iterator interface is not supported due to security
     * considerations. Calling it will always result in an an exception being
     * thrown.
     *
     * @throws UnsupportedOperationException if this method is called.
     */
    public void remove() {
        throw new UnsupportedOperationException();
    }
}