本文是 "
從薪水計算的例子看一段程序在不同環境中的變化 " 的續文.
如果需求發生如下變化:
如果說國家改變了公民福利制度,具體就是500元以下的每人補充300元,超過20000元的在原有基礎上再扣除20%,請問該如何編程?
具體等級稅率:
等級 稅率 額定扣除數
不超過500元 5% 0 (低保每人補助300元)
大于500小于2000 10% 25
大于2000小于5000 15% 125
大于5000小于20000 20% 375
超過20000元 25% 1375(在計算完的基礎上再乘以80%)
這時原有公式就不適用了,我們沒有必要回到分支語句的老路上去,將計算公式歸并成SalaryGrade的一個函數getSalaryAfterTax,然后從SalaryGrade分別擴展兩個類HigherSalaryGrade和LowerSalaryGrade,然后分別實現各自的getSalaryAfterTax函數即可.
代碼如下:
SalaryGrade類:
package com.sitinspring.oostyleadv;
/** *//**
* 工資等級類
* @author sitinspring(junglesong@gmail.com)
*
*/
public class SalaryGrade 
{
// 月薪界限
protected double grade;
// 稅率
protected double ratio;
// 折扣
protected double discount;
public SalaryGrade(double grade, double ratio, double discount) {
this.grade = grade;
this.ratio = ratio;
this.discount = discount;
}
public double getSalaryAfterTax(double salary){
return salary*(1-ratio)-discount;
}
public SalaryGrade() {
this(0.0f, 0.0f, 0.0f);
}
public double getDiscount() {
return discount;
}
public double getGrade() {
return grade;
}
public double getRatio() {
return ratio;
}
}
HigherSalaryGrade類:
package com.sitinspring.oostyleadv;
/** *//**
* 超高收入工資等級類
* @author sitinspring(junglesong@gmail.com)
*
*/
public class HigherSalaryGrade extends SalaryGrade{
public HigherSalaryGrade(double grade, double ratio, double discount) {
super(grade,ratio,discount);
}
public double getSalaryAfterTax(double salary){
return (salary*(1-ratio)-discount)*0.8;
}
public HigherSalaryGrade() {
this(0.0f, 0.0f, 0.0f);
}
}
LowerSalaryGrade類:
package com.sitinspring.oostyleadv;
/** *//**
* 低保工資等級類
* @author sitinspring(junglesong@gmail.com)
*
*/
public class LowerSalaryGrade extends SalaryGrade{
public LowerSalaryGrade(double grade, double ratio, double discount) {
super(grade,ratio,discount);
}
public double getSalaryAfterTax(double salary){
return salary*(1-ratio)-discount+300;
}
public LowerSalaryGrade() {
this(0.0f, 0.0f, 0.0f);
}
}
SalaryCaculator類:
package com.sitinspring.oostyleadv;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
/** *//**
* 工資計算類
* @author sitinspring(junglesong@gmail.com)
*
*/
public class SalaryCaculator{
private List<SalaryGrade> grades;
public SalaryCaculator(){
grades=new ArrayList<SalaryGrade>();
grades.add(new LowerSalaryGrade(500,0.05,0));
grades.add(new SalaryGrade(2000,0.1,25));
grades.add(new SalaryGrade(5000,0.15,125));
grades.add(new SalaryGrade(20000,0.20,375));
grades.add(new HigherSalaryGrade(99999999,0.25,1375));
}
// OO化的查詢方法
public double getSalaryAfterTax(double total){
SalaryGrade taxGrade=null;
for(Iterator it=grades.iterator();it.hasNext();){
taxGrade=(SalaryGrade)it.next();
if(total>taxGrade.getGrade()){
continue;
}
else{
break;
}
}
return taxGrade.getSalaryAfterTax(total);
}
}
Main:
package com.sitinspring.oostyleadv;
/** *//**
* Main函數所在的類
* @author sitinspring(junglesong@gmail.com)
*
*/
public class Main{
public static void main(String[] args){
SalaryCaculator caculator=new SalaryCaculator();
for(double total=100;total<30000;total+=1000){
System.out.println("稅前薪水="+total+" 稅后薪水="+caculator.getSalaryAfterTax(total));
}
}
}
代碼下載:
http://www.tkk7.com/Files/sitinspring/TaxCaculator20071115120519.rar