目录

工厂方法

# 工厂方法（Factory Method）

# Intent

定义了一个创建对象的接口，但由子类决定要实例化哪个类。工厂方法把实例化操作推迟到子类。

# Class Diagram

在简单工厂中，创建对象的是另一个类，而在工厂方法中，是由子类来创建对象。

下图中，Factory 有一个 factory() 方法，这个方法需要用到一个产品对象，这个产品对象由 factoryMethod() 方法创建。该方法是抽象的，需要由子类去实现。


# Implementation

package com.code.factory.example;

public abstract class Product {
    abstract public void onSay();
}
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package com.code.factory.example;

public class CommonProduct extends Product {
    public void onSay(){
        System.out.println(toString() + " : CommonProduct");
    }
}
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package com.code.factory.example;

public class MobileProduct extends Product {
    public void onSay(){
        System.out.println(toString() + " : MobileProduct");
    }
}
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package com.code.factory.example;

public class ComputerProduct extends Product {
    public void onSay(){
        System.out.println(toString() + " : ComputerProduct");
    }
}
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package com.code.factory.example;

public abstract class Factory {
    abstract protected Product factoryMethod();
    public Product factory() {
        return factoryMethod();
    }
}
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package com.code.factory.example;

public class MoblieFactory extends Factory {
    protected Product factoryMethod() {
        return new MobileProduct();
    }
}
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package com.code.factory.example;

public class ComputerFactory extends Factory {
    protected Product factoryMethod() {
        return new ComputerProduct();
    }
}
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package com.code.factory.example;

public class CommonFactory extends Factory {
    protected Product factoryMethod() {
        return new CommonProduct();
    }
}
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测试例子

package com.code.factory.example;

public class Main {
  
    public static void main(String[] args) {
        Factory factory;
        factory = new CommonFactory();
        Product commonFactory = factory.factory();
        commonFactory.onSay();

        factory = new MoblieFactory();
        Product mobileFactory = factory.factory();
        mobileFactory.onSay();

        factory = new ComputerFactory();
        Product computerFactory = factory.factory();
        computerFactory.onSay();
    }
}
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com.code.factory.example.CommonProduct@123a439b : CommonProduct
com.code.factory.example.MobileProduct@3c679bde : MobileProduct
com.code.factory.example.ComputerProduct@16b4a017 : ComputerProduct
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# JDK