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();}}