一个元素不可修改的迭代器

/*

 * Distributed as part of mchange-commons-java 0.2.9

 *

 * Copyright (C) 2015 Machinery For Change, Inc.

 *

 * Author: Steve Waldman <swaldman@mchange.com>

 *

 * This library is free software; you can redistribute it and/or modify

 * it under the terms of EITHER:

 *

 *     1) The GNU Lesser General Public License (LGPL), version 2.1, as 

 *        published by the Free Software Foundation

 *

 * OR

 *

 *     2) The Eclipse Public License (EPL), version 1.0

 *

 * You may choose which license to accept if you wish to redistribute

 * or modify this work. You may offer derivatives of this work

 * under the license you have chosen, or you may provide the same

 * choice of license which you have been offered here.

 *

 * This software is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

 *

 * You should have received copies of both LGPL v2.1 and EPL v1.0

 * along with this software; see the files LICENSE-EPL and LICENSE-LGPL.

 * If not, the text of these licenses are currently available at

 *

 * LGPL v2.1: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html

 *  EPL v1.0: http://www.eclipse.org/org/documents/epl-v10.php 

 * 

 */
 /*
 nowjava
 */

//package com.nowjava;

import java.util.*;


public class Main {

    public static Iterator oneElementUnmodifiableIterator(final Object elem) {

        return new Iterator() {

            boolean shot = false;


            public boolean hasNext() {

                return (!shot);

            }


            public Object next() {

                if (shot)

                    throw new NoSuchElementException();

                else {

                    shot = true;