简单工厂模式

一、定义

简单工厂提供一个创建对象的接口，负责其他类实例的创建，被创建的实例一般都具有共同的父类。

二、类图表示

三、实现

1、Product

package pattern.creational.factorymethod;

public interface Product {

}


package pattern.creational.factorymethod;

public class ConcreteProductA implements Product {

}


package pattern.creational.factorymethod;

public class ConcreteProductB implements Product {

}

2、Creator

package pattern.creational.factorymethod.simple;

import pattern.creational.factorymethod.ConcreteProductA;
import pattern.creational.factorymethod.ConcreteProductB;
import pattern.creational.factorymethod.Product;

public class Creator {

	private static Creator creator;
	
	private Creator() {}
	
	public synchronized static Creator getInstance(){
		if(creator == null){
			creator = new Creator();
		}
		return creator;
	}
	
	public Product factoryMethod(String type){
		Product product = null;
		switch(type){
			case "A":
				product = new ConcreteProductA();
				break;
			case "B":
				product = new ConcreteProductB();
				break;
		}
		return product;
	}
}

四、使用

package pattern.creational.factorymethod.simple;

import pattern.creational.factorymethod.Product;

public class Client {

	public static void main(String[] args) {
		Creator creator = Creator.getInstance();
		Product product = creator.factoryMethod("A");
		System.out.println("Created " + product.getClass().getSimpleName());
		product = creator.factoryMethod("B");
		System.out.println("Created " + product.getClass().getSimpleName());
	}
}

• 程序输出

Created ConcreteProductA

Created ConcreteProductB

五、优点与适用场合

1、优点

• 将对象的创建和使用分离
• 减少代码的重复(统一使用工厂创建对象)

2、使用场合

• 对象的实例化过程很复杂或对象的创建过程容易发生变化