易学设计模式八 工厂方法（Factory Method）

工厂方法模式的用意是定义一个创建产品对象的工厂，将实际的创建工作推迟到子类中。




修改上节中简单工厂模式

抽象工厂

public interface FruitGardener {
	public Fruit factory();
}

具体工厂

public class AppleGardener implements FruitGardener {
	public Fruit factory() {
		return new Apple();
	}
}

public class GrapeGardener implements FruitGardener {
	public Fruit factory() {
		return new Grape();
	}
}

public class StrawberryGardener implements FruitGardener {
	public Fruit factory() {
		return new Strawberry();
	}
}

其他类请参照，上一篇博客，简单工厂模式

测试类

public class Client {
	public static void main(String[] args) {	
		FruitGardener ag = new AppleGardener();
		Fruit apple = ag.factory();
		apple.plant();
		apple.grow();
		apple.harvest();
		FruitGardener gg = new GrapeGardener();
		Fruit grape = gg.factory();
		grape.plant();
	}
}

输出结果：

Apple has been planted
Apple is growing
Apple has been havested
Grape has been planted


URL 与 URLConnection的应用
URL hao360 = new URL("http://hao.360.cn/");
URLConnection hc = hao360.openConnection();
URLConnection是一个抽象类，所以hao360.openConnection()返回的一定是URLConnection的子类，所以openConnection()是工厂方法。

public class URLConnectionReader {

	public static void main(String[] args) throws Exception {
		URL hao360 = new URL("http://hao.360.cn/");
		URLConnection hc = hao360.openConnection();
		BufferedReader in = new BufferedReader(
				new InputStreamReader(hc.getInputStream()));
		String inputLine;
		while((inputLine = in.readLine()) != null) {
			System.out.println(inputLine);
		}
		in.close();
	}
}