public class Test {

public static void main(String[] args) {

    HashSet hs = new HashSet();

    hs.add(new Person("a1",11));   //将Person类添加进Hashset里面

    Iterator it = hs.iterator();   //定义1个迭代器

    while(it.hasNext()) //开始遍历HashSet
       {
         System.out.println(it.next().getClass().toString());   //测试类型，结果为class Person

           Person p = (Person) it.next();   //编译通过

           Person p = it.next();           //编译报错
       }

}

}