toUpperCase()方法将字符串小写字符转换为大写
语法
效果图如下：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>用户登录</title>
<link href="../images/login.css" rel="stylesheet" type="text
