jsp开发模式和web计算器案例

package cn.itcast.domain;

import java.math.BigDecimal;

//封装计算器数据的bean
public class Calculator {

private String firstnum = "0";
private String secondnum = "0";
private char operator = '+';
private String 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("运算符只能+-*/");
}

}

public String getFirstnum() {
return firstnum;
}

public void setFirstnum(String firstnum) {
this.firstnum = firstnum;
}

public String getSecondnum() {
return secondnum;
}

public void setSecondnum(String secondnum) {
this.secondnum = secondnum;
}

public char getOperator() {
return operator;
}

public void setOperator(char operator) {
this.operator = operator;
}

public String getResult() {
return result;
}

public void setResult(String result) {
this.result = result;
}
}