sql 删除表格里面的用户和修改密码的问题

package com.demo.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import com.mysql.jdbc.PreparedStatement;

public class JdbcConnectMain {

    public static void main(String[] args) throws Exception, IllegalAccessException, ClassNotFoundException, SQLException {
        Class.forName("com.mysql.jdbc.Driver").newInstance();
        
        Connection con = java.sql.DriverManager
                .getConnection(
                        "jdbc:mysql://localhost/test?useUnicode=true&characterEncoding=GBK",
                        "root", "123456");
        readDataFromDB(con);
        
        insertInto(con);
        
        // delete,update
        // badqiu的密码改成为123456；用到数据库的UPDATE功能
        // 把用户名jz删除
    }

    private static void insertInto(Connection con) throws SQLException {
        java.sql.PreparedStatement ps = con.prepareStatement("insert into user(username,pwd) values (?,?)");
        ps.setString(1, System.currentTimeMillis()+"");
        ps.setString(2, "pwd_123456");
        ps.execute();
    }

    private static void readDataFromDB(Connection con) throws SQLException {
        Statement stmt = null;
        ResultSet rst = null;
        
        try {
            stmt = con.createStatement();
            rst = stmt.executeQuery("select * from user");
            
            while(rst.next()) {
                System.out.println("username:"+rst.getString(1)+" pwd:"+rst.getString("pwd"));
            }
        }finally {
            stmt.close();
            rst.close();
        }
        
    }

}