代码：

 public static void main(String[] args) {Person2 person=new Person2("唐僧",new Horse());person.passRiver();person.onRoad();}

接口：

interface  Vehicles{public void work();
}

lass Horse implements Vehicles{@Overridepublic  void work() {System.out.println("大陆骑马去");}
}

class Boat implements  Vehicles{@Overridepublic void work() {System.out.println("过河坐船去");}
}

class Person2{private String name;private Vehicles Vehicles;public Person2(String name, Vehicles vehicles) {this.name = name;Vehicles = vehicles;}public void passRiver() {if (Vehicles == null) {Vehicles = VehiclesFactory.getBoat();}//过河，先从工厂获取一艘船Boat boat = VehiclesFactory.getBoat();boat.work();}public void onRoad () {//判断当前属性是否已经存在if (Vehicles == null) {Vehicles = VehiclesFactory.getHorse();}//过河，先从工厂获取一艘船Horse horse = VehiclesFactory.getHorse();horse.work();}}

public class VehiclesFactory {//写static，可以直接调用方法，不用创建对象public static Horse getHorse() {return new Horse();}public static Boat getBoat() {return new Boat();}
}

结果：