我這裏有一個問題，如果不能構成三角形，就應該不出現面積和周長，但是我寫不出來。
- 編寫兩個JSP頁面：inputTriangle.jsp與showTriangle.jsp。inputTriangle.jsp提供一個表單，用戶可以通過表單輸入三角形的三條邊提交給showTriangle.jsp。用戶提交表單後，JSP頁面將計算三角形面積和周長的任務交給一個bean去完成，創建bean的源文件是Triangle.java。頁面運行效果如圖所示。
(1) Triangle.java
package com.bean;
public class Triangle {
double a;
double b;
double c;
double rectangleArea;
double rectangleLength;
public Triangle() {
a=0.0;
b=0.0;
c=0.0;
}
public double getA() {
return a;
}
public void setA(double a) {
this.a = a;
}
public double getB() {
return b;
}
public void setB(double b) {
this.b = b;
}
public double getC() {
return c;
}
public void setC(double c) {
this.c = c;
}
public double getRectangleArea() {
double p=(a+b+c)/2;
double s=p*(p-a)*(p-b)*(p-c);
return Math.sqrt(s);
}
public double getRectangleLength() {
return a+b+c;
}
}
(2) inputTriangle.jsp
<%@ 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>
<form action="showTriangle.jsp">
輸入三角形三邊：<br>
邊A:<input type="text" name="A"><br>
邊B:<input type="text" name="B"><br>
邊C:<input type="text" name="C"><br>
<input type="submit" value="提交">
</form>
</body>
</html>
(3) showTriangle.jsp
<%@ 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>
<jsp:useBean id="one" class="com.bean.Triangle" scope="page"/>
<%
String A = request.getParameter("A");
String B =request.getParameter("B");
String C=request.getParameter("C");
double a=Double.parseDouble(A);
double b=Double.parseDouble(B);
double c=Double.parseDouble(C);
boolean m=false;
if(a>0&&b>0&&c>0&&(a+b)>c&&(a+c)>b&&(b+c)>a){
m=true;
}else{
m=false;
}
%>
<%one.setA(a);%>
<%one.setB(b);%>
<%one.setC(c);%>
三角形的三邊是：<br>
邊A：<%out.print(a); %>
邊B：<%out.print(b); %>
邊C：<%out.print(c); %>
<br>
這三個邊能構成一個三角形嗎？<%out.print(m); %>
<br>
面積是：<jsp:getProperty property="rectangleArea" name="one"/><br>
周長是：<jsp:getProperty property="rectangleLength" name="one"/>
</body>
</html>