[设计模式]之九:迭代器模式

//创建聚集类 保存列表 获取列表属性
public class ConcreteAggregate {

	private List<Object> items = new ArrayList<Object>();
	
	public int getCount() {
		return items.size();
	}
	
	public Object getItem(int index) {
		return items.get(index);
	}
	
	public void addItem(Object object) {
		items.add(object);
	}
}
//声明迭代器需要实现的接口
interface Iterator {
	public Object first();
	public Object next();
	public boolean isDone();
	public Object currentItem();
}
//具体的迭代类
public class ConcreteIterator implements Iterator {

	private ConcreteAggregate aggregate;
	private int current = 0;
	//需要聚集类的引用，保存item到列表
	public ConcreteIterator(ConcreteAggregate aggregate) {
		this.aggregate = aggregate;
	}
	
	@Override
	public Object first() {
		return aggregate.getItem(0);
	}

	@Override
	public Object next() {
		Object obj = null;
		current++;
		if (current < aggregate.getCount()) {
			obj = aggregate.getItem(current);
		}
		return obj;
	}

	@Override
	public boolean isDone() {
		return current >= aggregate.getCount() ? true : false;
	}

	@Override
	public Object currentItem() {
		return aggregate.getItem(current);
	}

}
//客户代码
public static void main(String[] args) {
	// TODO Auto-generated method stub
	ConcreteAggregate a = new ConcreteAggregate();
	
	a.addItem("Tom");
	a.addItem("Jerry");
	a.addItem("Jack");
	a.addItem("Rose");
	
	Iterator i = new ConcreteIterator(a);
	
	Object item = i.first();
	while(!i.isDone()) {
		System.out.println("Hello " + i.currentItem());
		i.next();
	}
}
//输出
Hello Tom
Hello Jerry
Hello Jack
Hello Rose