第一章.良好应用程序基石(2)

伟大软件的简易三步骤：

1.确认你的软件客户要它做的事。

2.运用基本的OO原则来增加软件的灵活性。

3.努力实现可维护、可重用的设计。

项目架构：

Guitar类：

package com.headfirst.guitar;

public class Guitar {
    private String serialNumber, builder, model, type, backWood, topWood;
    private double price;
    
    public Guitar(String serialNumber, double price, String builder, 
            String model, String type, String backWood, String topWood){
        this.serialNumber = serialNumber;
        this.price = price;
        this.builder = builder;
        this.model = model;
        this.type = type;
        this.backWood = backWood;
        this.topWood = topWood;
    }
    
    public String getSerialNumber(){
        return serialNumber;
    }
    public double getPrice(){
        return price;
    }
    public void setPrice(float newPrice){
        this.price = newPrice;
    }
    public String getBuilder(){
        return builder;
    }
    public String getModel(){
        return model;
    }
    public String getType(){
        return type;
    }
    public String getBackWood(){
        return backWood;
    }
    public String getTopWood(){
        return topWood;
    }
}

Inventory类：

package com.headfirst.guitar;

import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

public class Inventory {
    
    private List guitars;
    
    public Inventory(){
        guitars = new LinkedList();
    }
    
    public void addGuitar(String serialNumber, double price, String builder, String model, String type,
            String backWood, String topWood){
        Guitar guitar = new Guitar(serialNumber, price, builder, 
                model, type, backWood, topWood);
        guitars.add(guitar);
    }
    
    public Guitar getGuitar(String serialNumber){
        for(Iterator i = guitars.iterator(); i.hasNext();){
            Guitar guitar = (Guitar) i.next();
            if(guitar.getSerialNumber().equals(serialNumber)){
                return guitar;
            }
        }
        
        return null;
    }
    
    public Guitar search(Guitar searchGuitar){
        for(Iterator i = guitars.iterator(); i.hasNext();){
            Guitar guitar = (Guitar) i.next();
            String builder = searchGuitar.getBuilder();
            if((builder != null) && (!builder.equals("")) && 
                    (!builder.equals(guitar.getBuilder())))
                    continue;
            
            String model = searchGuitar.getModel();
            if((model != null) && (!model.equals("")) && 
                    (!model.equals(guitar.getModel())))
                    continue;
            
            String type = searchGuitar.getType();
            if((type != null) && (!type.equals("")) && 
                    (!type.equals(guitar.getType())))
                    continue;
            
            String backWood = searchGuitar.getBackWood();
            if((backWood != null) && (!backWood.equals("")) && 
                    (!backWood.equals(guitar.getBackWood())))
                    continue;
            
            String topWood = searchGuitar.getTopWood();
            if((topWood != null) && (!topWood.equals("")) && 
                    (!topWood.equals(guitar.getTopWood())))
                    continue;
            return guitar;
        }
        
        return null;
    }
}

搜寻测试代码：

package com.headfirst.guitar;

public class FindGuitarTester {
    public static void main(String[] args){
        Inventory inventory = new Inventory();
        initializeInventory(inventory);
        
        Guitar whatErinLikes = new Guitar("", 0, "fender", "Stratocastor", "electric", "Alder", "Alder");
        
        Guitar guitar = inventory.search(whatErinLikes);
        if(guitar != null){
            System.out.println("Erin, you might like this " + 
            guitar.getBuilder() + " " + guitar.getModel() + 
            " " + guitar.getType() + " guitar:
 " + 
            guitar.getBackWood() + " back and sides,
 " +
            guitar.getTopWood() + " top.
You can have it for only $" + 
            guitar.getPrice() + "!");
        }else{
            System.out.println("Sorry, Erin, we have nothing for you.");
        }
    }
    
    private static void initializeInventory(Inventory inventory){
        inventory.addGuitar("V95693", 1499.95, "Fender", "Stratocastor", "electric", "Alder", "Alder");
    }
}

运行结果：

为什么，明明有，为什么说没有?

检查了代码，可能搜寻中“fender”的f是小写，而我们有的“Fender”是大写。

好，我们对吉他搜索工具进行第一个改善，去除掉所有String比较：

项目修改架构：

Builder.java：

package com.headfirst.guitar;

public enum Builder {
    
    FENDER, MARTIN, GIBSON, COLLINGS, OLSON, RYAN, PRS, ANY;
    
    public String toString(){
        switch(this){
        case FENDER:
            return "Fender";
        case MARTIN:
            return "Martin";
        case GIBSON:
            return "Gibson";
        case COLLINGS:
            return "Collings";
        case OLSON:
            return "Olson";
        case RYAN:
            return "Ryan";
        case PRS:
            return "Prs";
        case ANY:
            return "Any";
        default: 
            return "";
        }
    }
}

Type.java：

package com.headfirst.guitar;

public enum Type {
    ACOUSTIC, ELECTRIC;
    
    public String toString(){
        switch(this){
        case ACOUSTIC: 
            return "acoustic";
        case ELECTRIC: 
            return "electric";
        default:
            return "";
        }
    }
}

Wood.java：

package com.headfirst.guitar;

public enum Wood {
    INDIAN_ROSEWOOD, BRAZILIAN_ROSEWOOD, ALDER;
    
    public String toString(){
        switch(this){
        case INDIAN_ROSEWOOD:
            return "Indian Rosewood";
        case BRAZILIAN_ROSEWOOD:
            return "Brazilian Rosewood";
        case ALDER:
            return "Alder";
        default:
            return "";
        }
    }
}

修改FindGuitarTester.java第8行代码：

 Guitar whatErinLikes = new Guitar("", 0, "Builder.FENDER", "Stratocastor", "Type.ELECTRIC", "Wood.ALDER", "Wood.ALDER"); 

修改Inventory.java中search()方法：

public Guitar search(Guitar searchGuitar){
        for(Iterator i = guitars.iterator(); i.hasNext();){
            Guitar guitar = (Guitar) i.next();
            
            if(searchGuitar.getBuilder() != guitar.getBuilder())
                    continue;
            
            String model = searchGuitar.getModel().toLowerCase();
            if((model != null) && (!model.equals("")) && 
                    (!model.equals(guitar.getModel().toLowerCase())))
                    continue;
            
            if(searchGuitar.getType() != guitar.getType())
                    continue;
            
            if(searchGuitar.getBackWood() != guitar.getBackWood())
                    continue;
            
            if(searchGuitar.getTopWood() != guitar.getTopWood())
                    continue;
            
            return guitar;
        }
        
        return null;
    }

现在我们担心的是Model属性，我们没有把它做成enum，并且Model没有办法限制，所以做不出enum。

除此之外：我们修改的地方还有：

各种变量的类型，用enum的全部替换掉。