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Voovan is a java framwork and it not depends on any third-party framework.

There is a newer version: 4.3.8

package org.voovan.tools.collection;

import java.util.ArrayList;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * 对象链
 *
 * @author helyho
 *
 * Voovan Framework.
 * WebSite: https://github.com/helyho/Voovan
 * Licence: Apache v2 License
 */
public class Chain  extends ArrayList {
	public ThreadLocal iteratorLocal = ThreadLocal.withInitial(()->new AtomicInteger(0));
	public ThreadLocal invertedIteratorLocal = ThreadLocal.withInitial(()->new AtomicInteger(0));
	private boolean isStop;

	/**
	 * 构造函数
	 */
	public Chain(){
		isStop = false;
		rewind();
	}

	/**
	 * 重置链的迭代器
	 * @return 链对象
	 */
	public Chain rewind(){
		isStop = false;
		iteratorLocal.get().set(0);
		invertedIteratorLocal.get().set(this.size() - 1);

		return this;
	}

	/**
	 * 迭代完成
	 */
	public void stop(){
		this.isStop = true;
	}

	/**
	 * 迭代器下一个元素
	 * @return 下一个元素
	 */
	public E next(){
		if(isStop){
			return null;
		} else {
			if(this.hasNext()){
				 E e = this.get(iteratorLocal.get().getAndIncrement());
				return e;
			} else {
				return null;
			}
		}
	}

	/**
	 * 迭代器是否有下一个对象
	 * @return 是否有下一个对象
	 */
	public boolean hasNext(){
		if(isStop){
			return false;
		} else {
			return iteratorLocal.get().get() <= this.size() - 1;
		}
	}

	/**
	 * 迭代器上一个元素
	 * @return 上一个元素
	 */
	public E previous(){
		if(isStop){
			return null;
		} else {
			if(this.hasPrevious()){
				return this.get(invertedIteratorLocal.get().getAndDecrement());
			} else {
				return null;
			}
		}
	}

	/**
	 * 迭代器是否有上一个对象
	 * @return 是否有上一个对象
	 */
	public boolean hasPrevious(){
		if(isStop){
			return false;
		} else {
			return invertedIteratorLocal.get().get() >= 0;
		}
	}

}