首先需要有一个封装计算数和计算的类
package cn.itcast.domain;
import java.math.BigDecimal;
// 封装计算的bean
public class CalculatorBean {
private String firstNum="0";
private char operator='+';
private String secondNum="0";
private String result;
public String getFirstNum() {
return firstNum;
}
public void setFirstNum(String firstNum) {
this.firstNum = firstNum;
}
public char getOperator() {
return operator;
}
public void setOperator(char operator) {
this.operator = operator;
}
public String getSecondNum() {
return secondNum;
}
public void setSecondNum(String secondNum) {
this.secondNum = secondNum;
}
public String getResult() {
return result;
}
public void setResult(String result) {
this.result = result;
}
public void calculate(){
BigDecimal first = new BigDecimal(this.firstNum);
BigDecimal second = new BigDecimal(this.secondNum);
switch (this.operator) {
case '+':
this.result = first.add(second).toString();
break;
case '-':
this.result = first.subtract(second).toString();
break;
case '*':
this.result = first.multiply(second).toString();
break;
case '/':
if(second.doubleValue()==0){
throw new RuntimeException("被除数不能为0");
}
this.result = first.divide(second,20,BigDecimal.ROUND_HALF_UP).toString();
break;
default:
throw new RuntimeException("运算符不正确");
}
}
}
然后再jsp页面计算和输出
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body style="text-align:center;">
<jsp:useBean id="CalculatorBean" class="cn.itcast.domain.CalculatorBean"></jsp:useBean>
<!-- 封装所有属性 -->
<jsp:setProperty property="*" name="CalculatorBean"/>
<%
try{
CalculatorBean.calculate();
}catch(Exception e){
out.write(e.getMessage());
}
%>
<hr>
计算结果是：
<jsp:getProperty property="firstNum" name="CalculatorBean"/>
<jsp:getProperty property="operator" name="CalculatorBean"/>
<jsp:getProperty property="secondNum" name="CalculatorBean"/>
=
<jsp:getProperty property="result" name="CalculatorBean"/>
<hr>
<form action="/day08/calculator.jsp" method="post">
<table width="40%" border="1" align="center">
<tr>
<td colspan="2">简单的计算器</td>
</tr>
<tr>
<td>第一个数</td>
<td>
<input type="text" name="firstNum">
</td>
</tr>
<tr>
<td>操作符</td>
<td>
<select name="operator">
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
</td>
</tr>
<tr>
<td>第二个数</td>
<td>
<input type="text" name="secondNum">
</td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="计算">
</td>
</tr>
</table>
</form>
</body>
</html>
结果是
可用于计算