GetArea.tag
<%@ tag import="java.text.DecimalFormat" %>
<%@tag pageEncoding="UTF-8"%>
<%@attribute name="numberA" required="true"%>
<%@attribute name="numberB" required="true"%>
<%@attribute name="numberC" required="true"%>
<%@attribute name="radio" required="true"%>
<%@variable name-given="area" variable-class="java.lang.Double" scope="AT_END"%>
<%@variable name-given="df" variable-class="java.text.DecimalFormat" scope="AT_END"%>
<%@variable name-given="message" scope="AT_END"%>
<%!
public double getArea(double a,double b,double c) {
if (a + b > c && a + c > b && b + c > a ) {
double p = (a + b + c)/2.0;
double area = Math.sqrt(p*(p-a)*(p-b)*(p-c));
return area;
}
return -1;
}
public double change(double num,String str) {
DecimalFormat df = new DecimalFormat("#." + str);
String format = df.format(num);
double value = Double.valueOf(format);
return value;
}
%>
<%
try {
double a = Double.parseDouble(numberA);
double b = Double.parseDouble(numberB);
double c = Double.parseDouble(numberC);
double result = 0;
result = getArea(a,b,c);
if (radio.equals("three")) {
double result1 = change(result, "000");
jspContext.setAttribute("area", result1);
jspContext.setAttribute("message", "三角形面积:");
}
if (radio.equals("six")) {
double result1 = change(result, "000000");
jspContext.setAttribute("area", result1);
jspContext.setAttribute("message", "三角形面积:");
}
} catch (Exception e) {
jspContext.setAttribute("area",new Double(-1.0));
jspContext.setAttribute("message",""+e.toString());
}
%>
one.jsp
<%--
Created by IntelliJ IDEA.
User: Hotin
Date: 2019/3/28
Time: 10:21
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib tagdir="/WEB-INF/tags" prefix="tag"%>
<html>
<head>
<title>one.jsp</title>
</head>
<body bgcolor="#6495ed">
<form action="" method="post">
<table>
<th>one</th>
<tr>
<td>输入数值A:</td>
<td><input type="text" name="a" placeholder="请输入数值a..."></td>
</tr>
<tr>
<td>输入数值B:</td>
<td><input type="text" name="b" placeholder="请输入数值b..."></td>
</tr>
<tr>
<td>输入数值C:</td>
<td><input type="text" name="c" placeholder="请输入数值c..."></td>
</tr>
<tr>
<td>格式:</td>
<td><input type="radio" name="rd" value="three">0.000</td>
<td><input type="radio" name="rd" value="six">0.000000</td>
</tr>
<tr>
<td><input type="submit" name="sb" value="提交"></td>
</tr>
</table>
</form>
<%
String a = request.getParameter("a");
String b = request.getParameter("b");
String c = request.getParameter("c");
String r = request.getParameter("rd");
if (a == null || b == null || c == null) {
a = "0";
b = "0";
c = "c";
}
if (a.length() > 0 && b.length() > 0 && c.length() >0) { %>
<tag:GetArea numberA="<%=a%>" numberB="<%=b%>" numberC="<%=c%>" radio="<%=r%>"/> <br>
<table>
<tr>
<td><%=message%></td>
<td><%=area%></td>
</tr>
</table>
<%}%>
</body>
</html>
运行结果
- 小数点后三位数运算结果
-小数点后六位数运算结果
