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  • 第一章.良好应用程序基石(3)

    客户又通知我们,他的Guitars库中有很多相同属性的吉他,但是可能售价上不同。

    现在,我们要实现的是,怎样返回库中能匹配所有属性的Guitar,并列出来。

    更新Inventory.java中的search()方法:

     1 public List search(Guitar searchGuitar){
     2         List matchingGuitars = new LinkedList();
     3         for(Iterator i = guitars.iterator(); i.hasNext();){
     4             Guitar guitar = (Guitar) i.next();
     5             
     6             if(searchGuitar.getBuilder() != guitar.getBuilder())
     7                     continue;
     8             
     9             String model = searchGuitar.getModel().toLowerCase();
    10             if((model != null) && (!model.equals("")) && 
    11                     (!model.equals(guitar.getModel().toLowerCase())))
    12                     continue;
    13             
    14             if(searchGuitar.getType() != guitar.getType())
    15                     continue;
    16             
    17             if(searchGuitar.getBackWood() != guitar.getBackWood())
    18                     continue;
    19             
    20             if(searchGuitar.getTopWood() != guitar.getTopWood())
    21                     continue;
    22             
    23             matchingGuitars.add(guitar);
    24         }
    25         
    26         return matchingGuitars;
    27     }

    更新FindGuitarTester.java:

     1 package com.headfirst.guitar;
     2 
     3 import java.util.Iterator;
     4 import java.util.List;
     5 
     6 public class FindGuitarTester {
     7     public static void main(String[] args){
     8         Inventory inventory = new Inventory();
     9         initializeInventory(inventory);
    10         
    11         Guitar whatErinLikes = new Guitar("", 0, Builder.FENDER, "Stratocastor", 
    12                 Type.ELECTRIC, Wood.ALDER, Wood.ALDER);
    13         
    14         List matchingGuitars = inventory.search(whatErinLikes);
    15         if(!matchingGuitars.isEmpty()){
    16             System.out.println("Erin, you might like these guitars: "); 
    17             for(Iterator i = matchingGuitars.iterator(); i.hasNext();){
    18                 Guitar guitar = (Guitar) i.next();
    19                 System.out.println("We have a " +
    20                 guitar.getBuilder() + " " + guitar.getModel() + " " + 
    21                 guitar.getType() + " guitar:
     " + 
    22                 guitar.getBackWood() + " back and sides,
     " +
    23                 guitar.getTopWood() + " top.
    You can have it for only $" + 
    24                 guitar.getPrice() + "!");
    25             }
    26         }else{
    27             System.out.println("Sorry, Erin, we have nothing for you.");
    28         }
    29     }
    30     
    31     private static void initializeInventory(Inventory inventory){
    32         inventory.addGuitar("V95693", 1499.95, Builder.FENDER, "Stratocastor", Type.ELECTRIC, Wood.ALDER, Wood.ALDER);
    33         inventory.addGuitar("B1234", 1600.35, Builder.FENDER, "Stratocastor", Type.ELECTRIC, Wood.ALDER, Wood.ALDER);
    34     }
    35 }

    通过以上的修改,我们完成了步骤一:确认你的软件做客户要它做的事。

    我们开始步骤二:运用基本的OO原则来增加软件的灵活性。

    1.对象应该做其名称所指之事。

    2.每个对象应该代表单一概念。

    3.未使用的特性是无用的赠品。

    4.任何时候,看到重复的代码,就找个地方进行封装。

    Inventory.java中的search()方法,需要改进的地方就是,用户不必传入一个Guitar对象,因为Guitar里的变量不全是用来搜索的,比如价格、序号用户是不知道的。

    所以,我们要从Guitar类中分割出来一个类,专门用来存储用户搜索数据。

    项目架构:

    Guitar.java:

     1 package com.headfirst.guitar;
     2 
     3 public class Guitar {
     4     private String serialNumber;
     5     private double price;
     6     private GuitarSpec guitarSpec;
     7     
     8     public Guitar(String serialNumber, double price, GuitarSpec guitarSpec){
     9         this.serialNumber = serialNumber;
    10         this.price = price;
    11         this.guitarSpec = guitarSpec;
    12     }
    13     
    14     public String getSerialNumber(){
    15         return serialNumber;
    16     }
    17     public double getPrice(){
    18         return price;
    19     }
    20     public void setPrice(float newPrice){
    21         this.price = newPrice;
    22     }
    23     public GuitarSpec getGuitarSpec(){
    24         return guitarSpec;
    25     }
    26 }

    GuitarSpec.java:

     1 package com.headfirst.guitar;
     2 
     3 public class GuitarSpec {
     4     Builder builder;
     5     String model;
     6     Type type;
     7     Wood backWood;
     8     Wood topWood;
     9     
    10     public GuitarSpec(Builder builder, String model, Type type, Wood backWood, Wood topWood){
    11         this.builder = builder;
    12         this.model = model;
    13         this.type = type;
    14         this.backWood = backWood;
    15         this.topWood = topWood;
    16     }
    17     
    18     public Builder getBuilder(){
    19         return this.builder;
    20     }
    21     
    22     public String getModel(){
    23         return this.model;
    24     }
    25     
    26     public Type getType(){
    27         return this.type;
    28     }
    29     
    30     public Wood getBackWood(){
    31         return this.backWood;
    32     }
    33     
    34     public Wood getTopWood(){
    35         return this.topWood;
    36     }
    37 }

    Inventory.java 修改:

     1 package com.headfirst.guitar;
     2 
     3 import java.util.Iterator;
     4 import java.util.LinkedList;
     5 import java.util.List;
     6 
     7 public class Inventory {
     8     
     9     private List guitars;
    10     
    11     public Inventory(){
    12         guitars = new LinkedList();
    13     }
    14     
    15     public void addGuitar(String serialNumber, double price, GuitarSpec guitarSpec){
    16         Guitar guitar = new Guitar(serialNumber, price, guitarSpec);
    17         guitars.add(guitar);
    18     }
    19     
    20     public Guitar getGuitar(String serialNumber){
    21         for(Iterator i = guitars.iterator(); i.hasNext();){
    22             Guitar guitar = (Guitar) i.next();
    23             if(guitar.getSerialNumber().equals(serialNumber)){
    24                 return guitar;
    25             }
    26         }
    27         
    28         return null;
    29     }
    30     
    31     public List search(GuitarSpec searchGuitar){
    32         List matchingGuitars = new LinkedList();
    33         for(Iterator i = guitars.iterator(); i.hasNext();){
    34             Guitar guitar = (Guitar) i.next();
    35             GuitarSpec guitarSpec = guitar.getGuitarSpec();
    36             
    37             if(searchGuitar.getBuilder() != guitarSpec.getBuilder())
    38                     continue;
    39             
    40             String model = searchGuitar.getModel().toLowerCase();
    41             if((model != null) && (!model.equals("")) && 
    42                     (!model.equals(guitarSpec.getModel().toLowerCase())))
    43                     continue;
    44             
    45             if(searchGuitar.getType() != guitarSpec.getType())
    46                     continue;
    47             
    48             if(searchGuitar.getBackWood() != guitarSpec.getBackWood())
    49                     continue;
    50             
    51             if(searchGuitar.getTopWood() != guitarSpec.getTopWood())
    52                     continue;
    53             
    54             matchingGuitars.add(guitar);
    55         }
    56         
    57         return matchingGuitars;
    58     }
    59 }

    FindGuitarTester.java修改:

     1 package com.headfirst.guitar;
     2 
     3 import java.util.Iterator;
     4 import java.util.List;
     5 
     6 public class FindGuitarTester {
     7     public static void main(String[] args){
     8         Inventory inventory = new Inventory();
     9         initializeInventory(inventory);
    10         
    11         GuitarSpec whatErinLikes = new GuitarSpec(Builder.FENDER, "Stratocastor", Type.ELECTRIC, Wood.ALDER, Wood.ALDER);
    12         
    13         List matchingGuitars = inventory.search(whatErinLikes);
    14         if(!matchingGuitars.isEmpty()){
    15             System.out.println("Erin, you might like these guitars: "); 
    16             for(Iterator i = matchingGuitars.iterator(); i.hasNext();){
    17                 Guitar guitar = (Guitar) i.next();
    18                 GuitarSpec guitarSpec = guitar.getGuitarSpec();
    19                 System.out.println("We have a " +
    20                 guitarSpec.getBuilder() + " " + guitarSpec.getModel() + " " + 
    21                 guitarSpec.getType() + " guitar:
     " + 
    22                 guitarSpec.getBackWood() + " back and sides,
     " +
    23                 guitarSpec.getTopWood() + " top.
    You can have it for only $" + 
    24                 guitar.getPrice() + "!");
    25             }
    26         }else{
    27             System.out.println("Sorry, Erin, we have nothing for you.");
    28         }
    29     }
    30     
    31     private static void initializeInventory(Inventory inventory){
    32         GuitarSpec guitarSpec1 = new GuitarSpec(Builder.FENDER, "Stratocastor", Type.ELECTRIC, Wood.ALDER, Wood.ALDER);
    33         inventory.addGuitar("V95693", 1499.95, guitarSpec1);
    34         inventory.addGuitar("B1234", 1600.35, guitarSpec1);
    35     }
    36 }

    我们把Guitar类中给用户搜索用的变量,重新构造一个新的类GuitarSpec。

    这样Guitar类的功能就很单一了,就是存储Guitar对象,GuitarSpec类则是为了提供给用户搜索相关信息的。

    运行结果:

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  • 原文地址:https://www.cnblogs.com/lanshanxiao/p/7184084.html
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