<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
<div>
<form action="main.jsp">
<input type="number" id="cs1" name="R" placeholder="请输入圆的半径">
<input type="submit" value="确定">
</form>
</div>
<%
String R=request.getParameter("R");
if(R!=null){
double cr=Double.parseDouble(R);
double cs=cr*cr*3.14;
out.print("输入圆的半径为："+cr+"。得出圆的面积为"+cs);
request.setAttribute("cr", cr);
request.setAttribute("cs", cs);
}
%>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
<div>
<form action="main.jsp">
<input type="number" name="SD" placeholder="请输入梯形上底">
<input type="number" name="XD" placeholder="请输入梯形下底">
<input type="number" name="H" placeholder="请输入梯形的高">
<input type="submit" value="确定">
</form>
</div>
<%
String SD=request.getParameter("SD");
String XD=request.getParameter("XD");
String H=request.getParameter("H");
if(SD!=null&&XD!=null&&H!=null){
double sd=Double.parseDouble(SD);
double xd=Double.parseDouble(XD);
double h=Double.parseDouble(H);
double ls=(sd+xd)*h/2;
out.print("输入的梯形上底、下底、高分别为："+sd+"、"+xd+"、"+h+"。得出梯形的面积为："+ls);
request.setAttribute("sd", sd);
request.setAttribute("xd", xd);
request.setAttribute("h", h);
request.setAttribute("ls", ls);
}
%>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<%@ include file="circle.jsp" %>
<%@ include file="ladder.jsp" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
</body>
</html>
来源：https://www.cnblogs.com/DOCEAN/p/12561683.html