《重构》第一章示例 ― 体验重构的魔力 RefactorSample

       实验室已坐定了,环境和氛围很好,今天老师请来了北京卓尔的孙经理,聊了很多,最大的意外是,任老师是云计算出身,棒,java以后必定是要接触云计算的。

1个月了,没有认真写博客,也没有认真学习,数据库的学习进度1直拖拖拉拉到现在也没有弄定,sad。。。接了1个任务,写1个基于Web的实验室内部的管理系统,拿来练手,以后就是企业项目1个CC呼唤中心的1模块,对接卓尔,第1次接触实际项目,还甚么都不会,激动却又忐忑。但,再1起重新燃起了学习的热火,来吧。


今天,看了1下《重构》的第1章,深深的被吸引了….

Let‘s go,1起走进重构的世界吧!


示例 

情形:顾客租电影,电影分3种,儿童票,普通片,新片,儿童片2天之内1.5元,超过两天,每天加收1.5元,普通片3天之内2元,超过两天,每天加收2元,新片每天3元,每租1次电影积分加1,如果是新片,且租期超过2天,积分加2。

分析:

以面向对象的思想分析,触及对象顾客,影片,外加1个租赁类作为顾客和影片的桥接

编写代码

影片类(Movie):

public class Movie {
public static final int CHILDRENS = 0;
public static final int REGULARS = 1;
public static final int NEW_RELEASE = 2;
private String name;
private int movType;

public Movie(String name, int movType) {
this.name = name;
this.movType = movType;
}

name: set 和 get 方法
movType: set 和get 方法
}

为了节省篇幅,Movie类的name、movType的set和get就不贴了。

租赁类(Rental):

public class Rental {
private Movie movie;
private int rentDays;

public Rental(Movie movie,int rentDays) {
this.movie = movie; this.rentDays = rentDays;
}

movie 和 rentDays的set和get方法


顾客类(Customer):

public class Customer {
private String name;
private ArrayList<Rental> rentals = new ArrayList<Rental>();

public Customer(String name) {
this.name = name;
}
public void addRent(Rental r){
rentals.add(r);
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String statement() throws Exception {
String result = "Rental report for " + getName() + "
";
double totalAmount = 0;
int frequent = 0;
for(Rental r : rentals){
double thisAmount = 0;
switch (r.getMovie().getMovType()){
case Movie.CHILDRENS :
thisAmount += (r.getRentDays()>2)?((r.getRentDays()⑵)*1.5+1.5):1.5;
break;
case Movie.REGULARS:
thisAmount += (r.getRentDays()>3)?((r.getRentDays()⑶)*2+2):2;
break;
case Movie.NEW_RELEASE:
thisAmount += r.getRentDays() * 3;
break;
default:throw new Exception("类型异常");

}
totalAmount += thisAmount;
frequent += (r.getMovie().getMovType()==Movie.NEW_RELEASE &&
r.getRentDays()>2)?2:1;
result+=" " + r.getMovie().getName() + " " + String.valueOf(thisAmount) + "
";
}
result += "Amount is " + String.valueOf(totalAmount) + "元
";
result += "frequent is " + String.valueOf(frequent)+"分";
return result;
}
}

编写测试代码:

public class Test {
public static void main(String[] args) throws Exception {
Movie m1 = new Movie("葫芦娃",0);//儿童片
Movie m2 = new Movie("神雕侠侣",1);//普通片
Movie m3 = new Movie("何以笙箫默",2);//新片
Customer c = new Customer("朱小妹");
c.addRent(new Rental(m1,2));//1.5
c.addRent(new Rental(m2,2));//2
c.addRent(new Rental(m3,3));//9
System.out.println(c.statement());
}
}

以上代码完成了示例需求,但是代码写的…太烂了,我自己写绝对也是这个模样。。。代码烂,怎样办?重构!

第1步:1劳永逸 ―  修改测试代码


为了方便测试,我们将打印结果作为1个字符串保存起来。

public class Test {
public static void main(String[] args) throws Exception {
Movie m1 = new Movie("葫芦娃",0);//儿童片
Movie m2 = new Movie("神雕侠侣",1);//普通片
Movie m3 = new Movie("何以笙箫默",2);//新片
Customer c = new Customer("朱小妹");
c.addRent(new Rental(m1,2));//1.5
c.addRent(new Rental(m2,2));//2
c.addRent(new Rental(m3,3));//9
String result = "Rental report for 朱小妹
" +
" 葫芦娃 1.5
" +
" 神雕侠侣 2.0
" +
" 何以笙箫默 9.0
" +
"Amount is 12.5元
" +
"frequent is 4分";
System.out.println(c.statement().equals(result));
}
}

以后的测试结果,true就是修改正确,false就是修改失败。


第2步:1石2鸟  ―  分解customer类statement方法


纵观所有代码,惟独customer类的statement代码最多,最乱,看着烦,看switch更烦,而switch的作用就是1个计算1个临时变量thisAmount的作用,而临时变量越多对1个程序来讲就越容易出错,既然容易出错,totalAmount和frement有甚么用,还占地方,留它们干吗,拿走,单独封装。

更改后的customer类:

public class Customer {
private String name;
private ArrayList<Rental> rentals = new ArrayList<Rental>();

public Customer(String name) {
this.name = name;
}
public void addRent(Rental r){
rentals.add(r);
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String statement() throws Exception {
String result = "Rental report for " + getName() + "
";
for (Rental r : rentals ) {
result += " " + r.getMovie().getName() + " " + String.valueOf(amountFor(r)) + "
";
}
result += "Amount is " + String.valueOf(getTotalAmount()) + "元
";
result += "frequent is " + String.valueOf(getTotalFrequent())+"分";
return result;
}
private double getTotalAmount() throws Exception {
double totalAmount = 0;
for(Rental r : rentals){
totalAmount += amountFor(r);
}
return totalAmount;
}
private int getTotalFrequent(){
int frequent = 0;
for(Rental r : rentals){
frequent += (r.getMovie().getMovType()==Movie.NEW_RELEASE &&
r.getRentDays()>2)?2:1;
}
return frequent;
}
private double amountFor(Rental r) throws Exception {
double thisAmount = 0;
switch (r.getMovie().getMovType()){
case Movie.CHILDRENS :
thisAmount += (r.getRentDays()>2)?((r.getRentDays()⑵)*1.5+1.5):1.5;
break;
case Movie.REGULARS:
thisAmount += (r.getRentDays()>3)?((r.getRentDays()⑶)*2+2):2;
break;
case Movie.NEW_RELEASE:
thisAmount += r.getRentDays() * 3;
break;
default:throw new Exception("类型异常");
}
return thisAmount;
}
}

这样statement方法庞大和临时变量多的问题都解决了,进行测试,true,修改正确

第3步:各回各家 ― 做自己该干的事


重新审视1下customer类,你会发现它很多它不该干的事,switch计算单次租赁花费和积分这个事,应当电影类干吧,花多钱,很多少分,电影本身最清楚

问题还是存在switch身上,最好不要在另外一个对象的属性基础上应用switch,如果非要使用,也应当是在对象自己的数据上使用,而不是在他人的数据上使用。

在rental类中增加getOneMoney方法和getOneFre方法,customer类删除amountFor方法,修改getTotalFrequent方法,switch搬家到Movie类中


更改后的customer类

只变动了getTotalFrequent方法for循环

public class Customer {
private String name;
private ArrayList<Rental> rentals = new ArrayList<Rental>();

public Customer(String name) {
this.name = name;
}
public void addRent(Rental r){
rentals.add(r);
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String statement() throws Exception {
String result = "Rental report for " + getName() + "
";
for (Rental r : rentals ) {
result += " " + r.getMovie().getName() + " " + String.valueOf(r.getOne()) + "
";
}
result += "Amount is " + String.valueOf(getTotalAmount()) + "元
";
result += "frequent is " + String.valueOf(getTotalFrequent())+"分";
return result;
}
private double getTotalAmount() throws Exception {
double totalAmount = 0;
for(Rental r : rentals){
totalAmount += r.getOne();
}
return totalAmount;
}
private int getTotalFrequent(){
int frequent = 0;
for(Rental r : rentals){
frequent += r.getOneFre();
}
return frequent;
}
}


更改后的rental,起了1个桥梁作用

public class Rental {
private Movie movie;
private int rentDays;
public Rental(Movie movie,int rentDays) {
this.movie = movie; this.rentDays = rentDays;
}
public int getRentDays() {
return rentDays;
}
public void setRentDays(int rentDays) {
this.rentDays = rentDays;
}
public Movie getMovie() {

return movie;
}
public double getOne() throws Exception {
return getMovie().getMoney(rentDays) ;
}
public int getOneFre(){
return getMovie().getFrequent(rentDays);
}
public void setMovie(Movie movie) {
this.movie = movie;
}
}

更改后的movie类,终究开始做事了

/**
* Created by Kevy on 2015/1/21.
*/
/*编写电影类代码*/
public class Movie {
public static final int CHILDRENS = 0;
public static final int REGULARS = 1;
public static final int NEW_RELEASE = 2;
private String name;
private int movType;

public Movie(String name, int movType) {
this.name = name;
this.movType = movType;
}

public int getMovType() {
return movType;
}
public void setMovType(int movType) {
this.movType = movType;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}

public double getMoney(int RentDays) throws Exception {
double thisAmount = 0;
switch (getMovType()){
case Movie.CHILDRENS :
thisAmount += (RentDays>2)?((RentDays⑵)*1.5+1.5):1.5;
break;
case Movie.REGULARS:
thisAmount += (RentDays>3)?((RentDays⑶)*2+2):2;
break;
case Movie.NEW_RELEASE:
thisAmount += RentDays * 3;
break;
default:throw new Exception("类型异常");
}
return thisAmount ;
}

public int getFrequent(int RentDays){
return (getMovType()==NEW_RELEASE &&
RentDays>2)?2:1;
}
}

测试OK,没有问题。


第4步 利用多态

现在所有的类,都在干自己的事,movie类的getMoney方法的代码量看着还是不太好,既然是3种电影只是类型不同而已,那末久完全可以向上抽取使用抽象类

public interface Type {
public int getType();
public double getMovMeony(int days);
}

public class ChildrenMov implements Type {

public int getType() {
return 0;
}

public double getMovMeony(int days) {
return (days>2)?((days⑵)*1.5+1.5):1.5;
}
}

public class RegularMov implements Type {

public int getType() {
return 1;
}

public double getMovMeony(int days) {
return (days>3)?((days⑶)*2+2):2;
}
}

public class NewMov implements Type {
public int getType() {
return 2;
}

public double getMovMeony(int days) {
return days * 3;
}
}

终究完全代码:

import java.util.ArrayList;

/**
* Created by Kevy on 2015/1/21.
*/
public class Customer {
private String name;
private ArrayList<Rental> rentals = new ArrayList<Rental>();

public Customer(String name) {
this.name = name;
}
public void addRent(Rental r){
rentals.add(r);
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String statement() throws Exception {
String result = "Rental report for " + getName() + "
";
for (Rental r : rentals ) {
result += " " + r.getMovie().getName() + " " + String.valueOf(r.getOne()) + "
";
}
result += "Amount is " + String.valueOf(getTotalAmount()) + "元
";
result += "frequent is " + String.valueOf(getTotalFrequent())+"分";
return result;
}
private double getTotalAmount() throws Exception {
double totalAmount = 0;
for(Rental r : rentals){
totalAmount += r.getOne();
}
return totalAmount;
}
private int getTotalFrequent(){
int frequent = 0;
for(Rental r : rentals){
frequent += r.getOneFre();
}
return frequent;
}
}

/**
* Created by Kevy on 2015/1/21.
*/

public class Rental {
private Movie movie;
private int rentDays;
public Rental(Movie movie,int rentDays) {
this.movie = movie; this.rentDays = rentDays;
}
public int getRentDays() {
return rentDays;
}
public void setRentDays(int rentDays) {
this.rentDays = rentDays;
}
public Movie getMovie() {

return movie;
}
public double getOne() throws Exception {
return getMovie().getMoney(rentDays) ;
}
public int getOneFre(){
return getMovie().getFrequent(rentDays);
}
public void setMovie(Movie movie) {
this.movie = movie;
}
}

/**
* Created by Kevy on 2015/1/21.
*/
/*编写电影类代码*/
public class Movie {
public static final int CHILDRENS = 0;
public static final int REGULARS = 1;
public static final int NEW_RELEASE = 2;
private String name;
private Type t;

public Movie(String name, int movType) throws Exception {
this.name = name;
setT(movType);
}

public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}

public double getMoney(int RentDays) {
return t.getMovMeony(RentDays);
}

public int getFrequent(int RentDays){
return (t.getType()==NEW_RELEASE &&
RentDays>2)?2:1;
}

public void setT(int d) throws Exception {
switch (d){
case CHILDRENS :t = new ChildrenMov();
break;
case REGULARS:t = new RegularMov();
break;
case NEW_RELEASE:t = new NewMov();
break;
default:throw new Exception("类型毛病");
}
}
}

import sun.plugin2.message.ModalityChangeMessage;

/**
* Created by Kevy on 2015/1/21.
*/

/* 编写测试代码 */
public class Test {
public static void main(String[] args) throws Exception {
Movie m1 = new Movie("葫芦娃",0);//儿童片
Movie m2 = new Movie("神雕侠侣",1);//普通片
Movie m3 = new Movie("何以笙箫默",2);//新片
Customer c = new Customer("朱小妹");
c.addRent(new Rental(m1,2));//1.5
c.addRent(new Rental(m2,2));//2
c.addRent(new Rental(m3,3));//9
String result = "Rental report for 朱小妹
" +
" 葫芦娃 1.5
" +
" 神雕侠侣 2.0
" +
" 何以笙箫默 9.0
" +
"Amount is 12.5元
" +
"frequent is 4分";
System.out.println(c.statement().equals(result));

}
}

至此,1个简单的代码重构示例,重构终了

重构最大的启发就是:测试、小改、测试、小改….

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波比源码 » 《重构》第一章示例 ― 体验重构的魔力 RefactorSample

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