！一个既简单又复杂的有关问题

public static List<ReceivedBean> getReceived(){        List<ReceivedBean> beans = null;        ReceivedBean bean = null;        Connection conn = null;        PreparedStatement pst = null;        ResultSet rs = null;        try {            conn = DBPoolConn.getConn();            String sql = "select * from db_customsms.dbo.tbl_smreceived";            pst = conn.prepareStatement(sql);            rs = pst.executeQuery();            while (rs.next()) {                                bean.setSm_id(rs.getInt("SM_ID"));                bean.setOrgaddr(rs.getString("orgaddr"));                bean.setDestaddr(rs.getString("destaddr"));                bean.setSm_content(rs.getString("sm_content"));                bean.setRecvtime(rs.getString("recvtime"));                bean.setReserve1(rs.getInt("reserve1"));                bean.setReserve2(rs.getString("reserve2"));                bean.setSmtype(rs.getInt("smtype"));                bean.setMessageid(rs.getString("messageid"));                bean.setOrgaddrtype(rs.getInt("orgaddrtype"));                bean.setActionid(rs.getInt("actionid"));                bean.setActionreasonid(rs.getInt("actionreasonid"));                bean.setServiceid(rs.getString("serviceid"));                bean.setProtocoltype(rs.getString("protocoltype"));                bean.setReaded(rs.getInt("readed"));                bean.setDroped(rs.getInt("droped"));                beans.add(bean);                System.out.println(bean.getSm_id());            }        } catch (SQLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally{            DBPoolConn.CloseAll(rs, pst, conn);        }        return beans;    }

Exception in thread "main" java.lang.NullPointerException    at com.chinagdn.services.SendMessage.getReceived(SendMessage.java:28)    at com.chinagdn.services.SendMessage.main(SendMessage.java:82)

while (rs.next()) {    bean = new ReceivedBean(); //还没new，当然是null了    bean.setSm_id(rs.getInt("SM_ID"));
------解决方案--------------------
bean 是空的。
bean  = new ReceivedBean();
------解决方案--------------------
ReceivedBean bean = null; 没初始化…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………