java+oracle初学提问

初学java，请教各位大侠：
出错信息：
返回的conn值：oracle.jdbc.driver.T4CConnection@1be5d1
java.sql.SQLException: 对只转发结果集的无效操作: last
at oracle.jdbc.driver.BaseResultSet.last(BaseResultSet.java:98)
at jdbc_oracle.getConnection(jdbc_oracle.java:27)
at jdbc_oracle.main(jdbc_oracle.java:52)
连接fail
返回的值：null----------------------
源代码：
//import java.beans.Statement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.PreparedStatement;
import java.util.Date;public class jdbc_oracle {
public static Connection getConnection() {
        Connection conn = null;  
        try {             
         Class.forName("oracle.jdbc.OracleDriver");  
            String url="jdbc:oracle:thin:@10.4.9.11:1521:orcl";  
            String user="ty";  
            String password="a123";  
            PreparedStatement pstm = null;
            try {  
                conn = DriverManager.getConnection(url,user,password);
                System.out.println("返回的conn值："+conn);  
                String sql = "select * from t_import_log";
                
                pstm =conn.prepareStatement(sql);
                //pstm =conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY); 
                
                ResultSet rs = pstm.executeQuery();
                rs.last();
                
                int rowcount = rs.getRow();
                System.out.println("jy_import_log:"+rowcount);
                
                return conn;              } catch (SQLException e) {  
             e.printStackTrace();  
            }  
        } catch (ClassNotFoundException e) {  
            e.printStackTrace();  
        } finally {  
            if (conn != null) {  
                try {  
                    conn.close();  
                } catch (SQLException e) {  
                    e.printStackTrace();  
                }  
            }  
        }  
        return null;  
    }  
  
    public static void main(String[] args) {  
        Connection conn = getConnection(); 
        if (conn != null) {  
            System.out.println("连接succ");  
            System.out.println("返回的值："+conn);
        } else {  
            System.out.println("连接fail");  
            System.out.println("返回的值："+conn);
        }  
    }  
       }