java.util.NoSuchElementException 异常

Iterator> it=stu_map.entrySet().iterator();
while(it.hasNext()){
String id=it.next().getKey();
Student s=it.next().getValue();
System.out.println(id+"姓名："+s.getName()+",年龄："+s.getAge());

}
java.util.NoSuchElementException

Map stu_map = new HashMap();
stu_map.put("id","1");
stu_map.put("s","pgy");

    Iterator it = stu_map.entrySet().iterator();
    while(it.hasNext()){
        Map.Entry<String,String> stu = (Map.Entry<String, String>) it.next();
        String id = stu.getKey();
        String s = stu.getValue();
        System.out.println(id+"姓名："+s);
    }

我把String id=it.next().getKey();删除之后就能正常，为什么会这样？

http://www.cnblogs.com/dennisac/archive/2012/03/30/2426074.html