public class IntegerDemo {
  public static void main(String[] args) {
    Factory factory = new DogFactory();
    Animal animal = factory.createAnimal();
    animal.eat();
 
    factory = new CatFactory();
    animal = factory.createAnimal();
    animal.eat();
  }
}
 
abstract class Animal {// 抽象类
  public abstract void eat();
}
 
class Dog extends Animal {// 狗
  public void eat() {
    System.out.println("a dog is eatting.");
  }
}
 
class Cat extends Animal {// 猫
  public void eat() {
    System.out.println("a cat is eatting.");
  }
}
 
interface Factory {// 接口
  public abstract Animal createAnimal();
}
 
class DogFactory implements Factory {// 实现接口
  public Animal createAnimal() {
    return new Dog();
  }
}
 
class CatFactory implements Factory {// 实现接口
  public Animal createAnimal() {
    return new Cat();
  }
}