index.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib tagdir="/WEB-INF/tags" prefix="Util" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>练习六</title>
</head>
<body>
<form action="" method= get>
<table>
<th>矩形(圆)面积计算器</th>
<tr>
<td>输入高a(半径r):</td>
<td><input type="text" name ="a" placeholder="请输入..."/></td>
</tr>
<tr>
<td>输入宽b:</td>
<td><input type="text" name ="b" placeholder="请输入..."/></td>
</tr>
</table>
<br><input type="submit" value = "提交"></input>
</form>
<% String a = request.getParameter("a");
String b = request.getParameter("b");
if (a == null||b == null) {
a = "0";
b = "0";