JavaWeb_jsp_简单计算器(jsp+javaBean模式)
BigDecimal演示
import java.math.BigDecimal;
public class BigDecimalDemo {
public static void main(String[] args) {
method_3();
}
private static void method_3() {
BigDecimal a=new BigDecimal("0.1");
BigDecimal b=new BigDecimal("0.006");
BigDecimal c1=a.add(b);
BigDecimal c2=a.subtract(b);
BigDecimal c3=a.multiply(b);
//除法必须指定小数位数（scale）,否则会报ArithmeticException
System.out.println(c1.toString());
//0.106
System.out.println(c2.toString());
//0.094
System.out.println(c3.toString());
//0.0006
BigDecimal c4=a.divide(b,10,BigDecimal.ROUND_CEILING);
System.out.println(c4.toString());
//16.6666666667
BigDecimal c5=a.divide(b,10,BigDecimal.ROUND_FLOOR);
System.out.println(c5.toString());
//16.6666666666
BigDecimal c6=a.divide(b,10,BigDecimal.ROUND_DOWN);
System.out.println(c6.toString());
//16.6666666666
BigDecimal c7=a.divide(b,10,BigDecimal.ROUND_UP);
System.out.println(c7.toString());
//16.6666666667
BigDecimal c8=a.divide(b,10,BigDecimal.ROUND_HALF_UP);
System.out.println(c8.toString());
//16.6666666667
BigDecimal c9=a.divide(b,10,BigDecimal.ROUND_HALF_DOWN);
System.out.println(c9.toString());
//16.6666666667
/*
static int ROUND_CEILING
接近正无穷大的舍入模式。
static int ROUND_FLOOR
接近负无穷大的舍入模式。
static int ROUND_UP
舍入远离零的舍入模式。
static int ROUND_DOWN
接近零的舍入模式。
static int ROUND_HALF_UP
向“最接近的”数字舍入，如果与两个相邻数字的距离相等，则为向上舍入的舍入模式。
static int ROUND_HALF_DOWN
向“最接近的”数字舍入，如果与两个相邻数字的距离相等，则为上舍入的舍入模式。
static int ROUND_HALF_EVEN
向“最接近的”数字舍入，如果与两个相邻数字的距离相等，则向相邻的偶数舍入。
static int ROUND_UNNECESSARY
断言请求的操作具有精确的结果，因此不需要舍入。
*/
}
private static void method_2() {
BigDecimal a=new BigDecimal(0.1);
BigDecimal b=new BigDecimal(0.006);
BigDecimal c=a.add(b);
System.out.println(c.toString());//直接传double照样出错
//0.10600000000000000567601521339611281291581690311431884765625
}
private static void method_1() {
double a=0.1;
double b=0.006;
System.out.println(a+b);
//0.10600000000000001
}
}
calculator.jsp负责显示数据和处理请求
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>计算器</title>
<style type="text/css" >
#calculate{
color: red;
}
</style>
</head>
<body style="text-align: center;">
第一种开发模式:JSP+JAVABEAN
jsp:既负责显示数据,又负责处理请求!
javaBean:专门封装数据
<jsp:useBean id="calc" class="cn.itcast.domain.CalculatorBean" scope="page" />
<jsp:setProperty name="calc" property="*"/>
<div id="calculate">
<%
try{
calc.calculate();
}catch(Exception e){
String str=e.getMessage();
out.write(str);
}
%>
</div>
<hr/>
计算结果是:${calc.firstNumber }${calc.operator }${calc.secondNumber }=${calc.result }
<hr/>
<form action="${pageContext.request.contextPath }/calculator.jsp" method="post">
<table width="40%" border="1">
<tr >
<td colspan="2" align="center">简单的计算器</td>
</tr>
<tr>
<td>第1个参数:</td>
<td>
<input type="text" name="firstNumber" />
</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2个参数:</td>
<td>
<input type="text" name="secondNumber" />
</td>
</tr>
<tr>
<td colspan="2" align="center">
<input type="submit" value="计算"/>
</td>
</tr>
</table>
</form>
</body>
</html>
CalculatorBean封装数据
package cn.itcast.domain;
import java.math.BigDecimal;
public class CalculatorBean {
private String firstNumber="0";
private char operator='+';
private String secondNumber="0";
private String result;
public void calculate(){
BigDecimal a=new BigDecimal(this.firstNumber);
BigDecimal b=new BigDecimal(this.secondNumber);
switch (this.operator) {
case '+':{
this.result=a.add(b).toString();
break;
}
case '-':{
this.result=a.subtract(b).toString();
break;
}
case '*':{
this.result=a.multiply(b).toString();
break;
}
case '/':{
if (b.doubleValue()==0) {
throw new RuntimeException("被除数不能为0");
}
this.result=a.divide(b,5,BigDecimal.ROUND_CEILING).toString();
break;
}
default:
throw new RuntimeException("运算符仅支持+-*/");
}
}
public String getFirstNumber() {
return firstNumber;
}
public void setFirstNumber(String firstNumber) {
this.firstNumber = firstNumber;
}
public char getOperator() {
return operator;
}
public void setOperator(char operator) {
this.operator = operator;
}
public String getSecondNumber() {
return secondNumber;
}
public void setSecondNumber(String secondNumber) {
this.secondNumber = secondNumber;
}
public String getResult() {
return result;
}
public void setResult(String result) {
this.result = result;
}
}