工厂模式

抽象动物：

java">public abstract class Animal {// 动物都要吃饭public abstract void eat();
}

java">public class Cat extends Animal{@Overridepublic void eat() {System.out.println("小猫吃猫粮");}
}

java">public class Cat extends Animal{@Overridepublic void eat() {System.out.println("小猫吃猫粮");}
}

抽象工厂：

java">public abstract class AnimalFactory {public abstract Animal createAnimal();
}

java">public class CatFacoty extends AnimalFactory{@Overridepublic Animal createAnimal() {return new Cat();}
}

java">public class DogFactory extends AnimalFactory{@Overridepublic Animal createAnimal() {return new Dog();}
}

java">public class FactoryTest {public static void main(String[] args) {AnimalFactory factory = new DogFactory();Animal animal = factory.createAnimal();animal.eat();AnimalFactory factory2 = new CatFacoty();Animal animal2 = factory2.createAnimal();animal2.eat();}
}

在这里，如果需要创建新的类，只需要新增animal的子类和factory的资料，不需要修改原来的代码，对扩展开放，符合开闭原则。

源码参考：

• Collection.iterator
• URLStreamHandler.createURLStreamHandler