设计模式-迭代器

定义：提供一种方法顺序访问一个聚合对象中的各个元素，而又不暴露其内部的表示。

UML类图：

interface Iterator {
    public Object next();
    public boolean hasNext();
}
class ConcreteIterator implements Iterator{
    private List list = new ArrayList();
    private int cursor =0;
    public ConcreteIterator(List list){
        this.list = list;
    }
    public boolean hasNext() {
        if(cursor==list.size()){
            return false;
        }
        return true;
    }
    public Object next() {
        Object obj = null;
        if(this.hasNext()){
            obj = this.list.get(cursor++);
        }
        return obj;
    }
}
interface Aggregate {
    public void add(Object obj);
    public void remove(Object obj);
    public Iterator iterator();
}
class ConcreteAggregate implements Aggregate {
    private List list = new ArrayList();
    public void add(Object obj) {
        list.add(obj);
    }
 
    public Iterator iterator() {
        return new ConcreteIterator(list);
    }
 
    public void remove(Object obj) {
        list.remove(obj);
    }
}
public class Client {
    public static void main(String[] args){
        Aggregate ag = new ConcreteAggregate();
        ag.add("小明");
        ag.add("小红");
        ag.add("小刚");
        Iterator it = ag.iterator();
        while(it.hasNext()){
            String str = (String)it.next();
            System.out.println(str);
        }
    }
}