行为模式－迭代子模式

迭代子模式：可以顺序的访问一个聚集中的元素而不必暴露聚集的内部表象

迭代子模式：主动迭代子和被动迭代子，也分别叫做内部迭代子 和外部迭代子

抽线迭代子

package com.javapatterns.iterator.whitebox;

public interface Iterator
{
    void first();

    void next();

    boolean isDone();

    Object currentItem();
}

 具体迭代子：

package com.javapatterns.iterator.whitebox;

public class ConcreteIterator implements Iterator
{
    /**
     * @directed 
     */
    private ConcreteAggregate agg;
	private int index = 0;
    private int size = 0;

    public ConcreteIterator(ConcreteAggregate agg)
    {
		this.agg = agg;
        size = agg.size();
        index = 0 ;
    }

    public void first()
    {
		index = 0 ;
    }

    public void next()
    {
		if (index < size)
        {
			index++;
        }
    }

    public boolean isDone()
    {
        return (index >= size);
    }

    public Object currentItem()
    {
        return agg.getElement(index);
    }
}

 抽象聚集：

package com.javapatterns.iterator.whitebox;

abstract public class Aggregate
{
    public Iterator createIterator()
    {
        return null;
    }
}

 

具体聚集：

package com.javapatterns.iterator.whitebox;

public class ConcreteAggregate extends Aggregate
{
    private Object objs[]= {"Monk Tang",
        "Monkey", "Pigsy",
        "Sandy", "Horse"};

    public Iterator createIterator()
    {
        return new ConcreteIterator(this);
    }

    public Object getElement(int index)
    {
		if (index < objs.length)
        {
			return objs[index];
        }
        else
        {
            return null;
        }
    }

    public int size()
    {
		return objs.length;
    }
}

 

客户端：

package com.javapatterns.iterator.whitebox;

public class Client {
	/**
	 * @directed
	 */
	private Iterator it;

	/**
	 * @directed
	 */
	private Aggregate agg = new ConcreteAggregate();

	public void operation() {
		it = agg.createIterator();

		while (!it.isDone()) {
			System.out.println(it.currentItem().toString());
			it.next();
		}
	}

	public static void main(String[] args) {
		Client client = new Client();
		client.operation();
	}
}