8、工厂方法

概念

• 定义一个创建对象的接口，让其子类自己决定实例化哪一个工厂类;
• 工厂模式使其创建过程延迟到子类进行;

demo

package com.cn.go.designpattern;

public class FactoryMethod {
    public static void main(String[] args) {
        MotorVehicleFactory motorVehicleFactory = new MotorVehicleFactory();
        Vehicle vehicle = motorVehicleFactory.create(Car.class);
        vehicle.move();

        NonMotorVehicleFactory nonMotorVehicleFactory = new NonMotorVehicleFactory();
        Vehicle bicycle = nonMotorVehicleFactory.create(Bicycle.class);
        bicycle.move();
    }
}

abstract class Vehicle{
   abstract void move();
}

class Car extends Vehicle{
    void move() {
        System.out.println("car move");
    }
}

class Bicycle extends Vehicle{

    void move() {
        System.out.println("bicycle move");
    }
}


/**
 * 这个类看似多余；没有这个类，直接创建对象的话就是 简单工厂
 */
abstract class VehicleFactory {
    abstract <T extends Vehicle> Vehicle create(Class<T> c);
}

class MotorVehicleFactory extends VehicleFactory{

    <T extends Vehicle> Vehicle create(Class<T> c) {
        T res =null ;
        try {
            res = (T) Class.forName(c.getName()).newInstance();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return res;
    }
}



class NonMotorVehicleFactory extends VehicleFactory{

    <T extends Vehicle> Vehicle create(Class<T> c) {
        Vehicle vehicle = null;

        try {
            vehicle =  c.newInstance();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return vehicle;
    }
}