JSP+JavaBean制作计算器

jsp代码：

    
    
    <%
        try{
            calcu.calculate();
        }catch(Exception e){
            out.write(e.getMessage());
        }
    %>
    
    
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    计算结果是：
    
    
    
    -
    
    
--------------------------------------------------------------------------------------------

    
    

    
    

        

            

                
简单的计算器
            
            

                
第一个参数
                

                    
                
            
            
            

                
操作符
                

                    
                        +
                        -
                        *
                        /
                    
                
            
            
            

                
第二个参数
                

                    
                
            
            
            

                

                    
                
            
        
        
    
    
    
    

java代码：

package second;

import java.math.BigDecimal;

public class CalculateBean {
    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(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("被除数不能为零");
                }
                this.result = first.divide(second, 20, BigDecimal.ROUND_HALF_UP).toString();
                break;
            }
            default:
                throw new RuntimeException("运算符只能为加减乘除");
        }
}
}