《大话设计模式》--工厂方法模式
题目:大学生和志愿者学雷锋,轮流去给孤寡老人送爱心
public class LeiFeng { public void sweep() { System.out.println("扫地"); } public void wash() { System.out.println("洗衣"); } public void buyRice() { System.out.println("买米"); } }
public class UnderGraduate extends LeiFeng {} public class Volunteer extends LeiFeng {}
public interface IFactory { LeiFeng createLeiFeng(); }
public class UnderGraduateFactory implements IFactory { @Override public LeiFeng createLeiFeng() { return new UnderGraduate(); } } public class VolunteerFactory implements IFactory { @Override public LeiFeng createLeiFeng() { return new Volunteer(); } }
public class Test { public static void main(String args[]) { IFactory factory = new PoliceFactory(); LeiFeng student = factory.createLeiFeng(); student.sweep(); student.wash(); student.buyRice(); } }
工厂类和方法类都要分别继承,工厂类用于生成新的对象。如果再加一个警察类,只需要下面这样做就可以了:
public class Police extends LeiFeng {} public class PoliceFactory implements IFactory { @Override public LeiFeng createLeiFeng() { return new Police(); } }
不需要动服务端,只需要在客户端Test中增加new PoliceFactory()就可以了
工厂方法模式和简单工厂模式的区别:
简单工厂模式只有一个工厂类,里面通过switch...case判断生成什么对象,如果增加了新的判断,就要修改服务端了,违背了开放-闭合原则。工厂方法模式有效的解决了这一问题。