迭代器模式
目前是一个已经没落的模式，基本上没人会单独写一个迭代器模式。
它提供一种方法访

//抽象迭代器
public interface Iterator {
	public Object next();
	public boolean hasNext();
	public boolean remove();
}
//具体迭代器
public class ConcreteIterator implements Iterator {
	private Vector<Object> vector = new Vector<Object>();
	private int cursor = 0 ;
	public ConcreteIterator(Vector<Object> vector) {
		super();
		this.vector = vector;
	}
	@Override
	public Object next() {
		Object result = null;
		if (this.hasNext()) {
			result=this.vector.get(cursor++);
		}else{
			result = null;
		}
		return result;
	}
	@Override
	public boolean hasNext() {
		if (this.cursor == vector.size() ) {
			return false;
		} else {
			return true;
		}
	}
	@Override
	public boolean remove() {
		this.vector.remove(this.cursor);
		return true;
	}
}
//抽象容器
public interface Aggregate {
	public void add(Object ob);
	public void remove(Object ob);
	public Iterator iterator();
}
//具体容器
public class ConcreteAggregate implements Aggregate {
	private Vector<Object> vector = new Vector<>();
	@Override
	public void add(Object ob) {
		this.vector.add(ob);
	}
	@Override
	public void remove(Object ob) {
		this.vector.remove(ob);
	}
	@Override
	public Iterator iterator() {
		return new ConcreteIterator(this.vector);
	}

}
public class Client {
	public static void main(String[] args) {
		Aggregate aggregate =new ConcreteAggregate();
		aggregate.add("abc");
		aggregate.add("bca");
		aggregate.add("er");
		Iterator iterator = aggregate.iterator();
		while(iterator.hasNext()){
			System.out.println(iterator.next());
		}
	}
}

问一个容器对象中的各个元素，而又不需要暴露该对象的内部细节。