出错代码如下：

static String u = "user";

static String p = "psw";

static String url = "jdbc:oracle:thin:@localhost:1521:db_name";

con = DriverManager.getConnection(url, u, p);

statement = con.createStatement();

String query1="select * from dm_mpg_test'";

ResultSet re1=statement.executeQuery(query1);

//get the number of the records

re1.last();

System.out.println("ResultSet size:"+re1.getRow());

报错java.sql.SQLException: 对只转发结果集的无效操作: last

需将statement定义成

statement = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_UPDATABLE);

允许结果集可移动。