package text6; import java.sql.*; public class inquire { Connection con; Statement cmd; ResultSet rs; private String url="jdbc:mysql://127.0.0.1:3306/student"; private String driver="com.mysql.jdbc.Driver"; public boolean validate (String uname,String upwd) { boolean flag=false; try { Class.forName(driver); con=DriverManager.getConnection(url,"root",""); cmd=con.createStatement(); String sql="select *from users"; rs=cmd.executeQuery(sql); if(rs.next()) if(rs.getString(1).equals(upwd))//数据库 flag=true; con.close(); }catch(Exception e) { flag=false; } return flag; } }改错

在该代码中，缺少一个右括号，应该在最后一行的 catch 语句块中加上一个右括号。同时，还需要在 catch 语句块中加上打印异常信息的代码，以便发现程序运行时可能出现的错误。以下是修改后的代码：

package text6;

import java.sql.*;

public class inquire {
    Connection con;
    Statement cmd;
    ResultSet rs;
    private String url = "jdbc:mysql://127.0.0.1:3306/student";
    private String driver = "com.mysql.jdbc.Driver";

    public boolean validate(String uname, String upwd) {
        boolean flag = false;
        try {
            Class.forName(driver);
            con = DriverManager.getConnection(url, "root", "");
            cmd = con.createStatement();
            String sql = "select * from users";
            rs = cmd.executeQuery(sql);
            if (rs.next())
                if (rs.getString(1).equals(upwd))//数据库
                    flag = true;
            con.close();
        } catch (Exception e) {
            flag = false;
            System.out.println("发生异常：" + e.getMessage());
        }
        return flag;
    }
}