Iterator(迭代器模式)--（超市管理者）

这个Iterator就是收银台干的活。

package patterns.actions.iterator;

public interface IteratorList {

	boolean isEmpty();//是否还有[hasNext()]

	Object nextMerchandise();//merchandise:商品

}

package patterns.actions.iterator;

/**
 * 收银台清点商品
 * @author one
 *
 */
public class IteratorCheck implements IteratorList {
	private Supermarket shop;

	private int total=0;

	private int current=0;

	IteratorCheck(Supermarket shop){
		this.shop=shop;
		this.total=shop.size();
		this.current=0;
	}

	@Override
	public boolean isEmpty() {
		return this.current<this.total;
	}

	@Override
	public Object nextMerchandise() {
		if(this.current<this.total)
			return this.shop.take(this.current++);
		return null;
	}

}

package patterns.actions.iterator;

/**
 * 购物的基本要素
 * @author one
 *
 */
public interface Shopping {

	public void buy(Object obj);//买新的产品[add]

	public IteratorList iteratorList();//结账[iterator]

}

package patterns.actions.iterator;

import java.util.ArrayList;
import java.util.List;

/**
 * 超市提供具体的购物环境
 *
 * @author one
 *
 */
public class Supermarket implements Shopping {
	private List cart = new ArrayList();// 购物车作为容器

	@Override
	public void buy(Object obj) {
		cart.add(obj);// 将商品放到购物车

	}

	@Override
	public IteratorList iteratorList() {
		return new IteratorCheck(this);
	}

	public int size() {
		return this.cart.size();
	}

	public Object take(int current) {
		if(current<this.cart.size())
			return this.cart.get(current);
		return null ;
	}
}

package patterns.actions.iterator;

public class Client {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Shopping cart = new Supermarket();
		cart.buy("可乐");
		cart.buy("果汁");
		cart.buy("酸梅");

		IteratorList check = cart.iteratorList();
		while (check.isEmpty()) {
			System.out.println(check.nextMerchandise());
		}

	}

}

输出结果：

可乐
果汁
酸梅