迭代器模式

摘自 《Java编程思想》第四版

 

/**
 * 迭代器模式
 * 
 * 利用非静态内部类可以访问外部类的特性
 * 
 * 摘自 Java编程思想 P192
 */

interface Selector{
	public boolean end();
	public Object current();
	public void next();
}

public class Sequence {

	private Object[] items;
	private int next = 0;
	public Sequence(int size){
		items = new Object[size];
	}
	public void add(Object x){
		if(next < items.length)
			items[next++] = x;
	}
	
	//内部类
	private class SequenceSelector implements Selector
	{
		private int i = 0;
		
		public boolean end() {
			return i==items.length;
		}

		public Object current() {
			return items[i];
		}

		public void next() {
			if(i<items.length)
				i++;
		}
	}
	
	public Selector selector()
	{
		return new SequenceSelector();
	}
	
	public static void main(String[] args) {
		Sequence sequence = new Sequence(10);
		for (int i = 0; i < 10; i++) {
			sequence.add(Integer.toString(i));
		}
		Selector selector = sequence.selector();
		while(!selector.end())
		{
			System.out.print(selector.current() + " ");
			selector.next();
		}
	}
}