使用jdbc查询postgres数据库遇到有关问题

package traffic;import java.sql.*;public class TrafficDatabaseCore  {        static void getConnection() throws SQLException, InstantiationException, IllegalAccessException, ClassNotFoundException    {        Class.forName("org.postgresql.Driver").newInstance();        Connection conn;        conn = DriverManager.getConnection("jdbc:postgresql://localhost:5432/traffic", "postgres", "******");        Statement st = conn.createStatement();        ResultSet rs = st.executeQuery("select * from test");        while(rs.next())        {            System.out.print(rs.getString(0));            System.out.println(rs.getInt(1));        }    }    }