很奇怪的vector

表中有2条记录
serialnumber
GS00000001
GS00000002

......
Vectorv=new Vector();
BeanBook beanbook =new BeanBook();
while(resultset.next())
{
    beanbook.setSerialnumber(resultset.getString("serialnumber"));
    v.add(beanorder);
}
Iterator it=v.iterator();
while(it.hasNext())
{
    beanbook=(BeanBook )it.next();
    System.out.println(beanbook.getSerialnumber());}
......

打印结果却是
GS00000002
GS00000002
一直没找出问题在哪！--!!