结果集不能与oracle一起使用

Question

Resultset每次都返回false并且循环没有被执行，任何人都可以帮我解决，我的代码如下所示

package db_final;

import java.sql.*;

public class sqlwork {

    static Statement st;
    static Connection connect;
    ResultSet rs;

    public String login(String sql, String user, String pass)  throws SQLException{
        String role = null;
        rs = st.executeQuery(sql);
        while (rs.next()){
            if(user.equalsIgnoreCase(rs.getString("username"))){
                if(pass.equalsIgnoreCase("password")){
                    role = rs.getString("role");
                    break;
                }
            }
        }
        return role;
    }
    public void connect() throws SQLException, ClassNotFoundException{
        Class.forName("oracle.jdbc.driver.OracleDriver");
        connect = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:final", "Omair", "12345");
        st = connect.createStatement();
    }