javaweb做一个计算器

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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beanpublic 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

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