简单工厂

public abstract class Animal {
public abstract void eat();
}

public class AnimalFactory {
/*public static Dog createDog() {
return new Dog();
}

public static Cat createCat() {
    return new Cat();
}*/

//发现方法会定义很多,复用性太差
//改进
public static Animal createAnimal(String name) {
    if("dog".equals(name)) {
        return new Dog();
    }else if("cat".equals(name)) {
        return new Cat();
    }else {
        return null;
    }
}

}

public class Cat extends Animal {

@Override
public void eat() {
    System.out.println("猫吃鱼");
}

}

public class Dog extends Animal {

@Override
public void eat() {
    System.out.println("狗吃肉");
}

}

public class Test {

/**
 * @param args
 */
public static void main(String[] args) {
    //Dog d = AnimalFactory.createDog();

    Dog d = (Dog) AnimalFactory.createAnimal("dog");
    d.eat();

    Cat c = (Cat) AnimalFactory.createAnimal("cat");
    c.eat();
}

}