[Design Pattern] 1.1 Factory Method Pattern Factory Method (Creation Type-Class)

Intent:Define an interface for creating objects and let subclasses decide which class to instantiate. Factory Method defers instantiation of a class (interface class) to its subclasses.

applicability:

When a class does not know the class of the object it must create. (The factory does not know whether to create product A or product B)

When a class wants its subclasses to specify the objects it creates. (Use factory A and factory B to create products)

When a class delegates the responsibility for object creation to one of multiple helper subclasses, and you want to localize the information about which helper subclass is the delegate.

Class Diagram:

/**
    工厂方法模式
/*
// FactoryMethod工厂方法类 
public class FactoryMethod{
	public static void main(String[] args){
        // 创建一个工厂
        Factory factoryA = new FactoryA();
        
        // 创建一个产品
		Product productA = factoryA.createProduct()  // 编译看=左边（是否有对应的方法），运行看=右边（实际是否有对应的方法）
		productA.info(); // 具体产品的方法




        // 创建一个工厂
        Factory factoryB = new FactoryB();
        
        // 创建一个产品
		Product productB = factoryB.createProduct()
		productB.info(); // 具体产品的方法

	}
}
 
// Product 产品接口
interface Product{
    public void info();
}

// ProductA 实现 Product 产品接口
class ProductA implements Product{
    // 实现抽象产品类中的抽象方法
	@Override
	public void info(){
		System.out.println("产品A")
	
	}
}

// ProductB 实现 Product 产品接口
class ProductB implements Product{
    // 实现抽象产品类中的抽象方法
	@Override
	public void info(){
		System.out.println("产品B")
	}
}

// Factory 工厂接口
interface Factory{
	public Product createProduct();
}

// FactoryA 实现 工厂接口
class FactoryA implements Factory{
      @Override
      public Product createProduct(){
        return new ProductA();
      }
}

// FactoryB 实现 工厂接口
class FactoryB implements Factory{
     @Override
      public Product createProduct(){
        return new ProductB();
      }
}