具体代码

//Travel.java
package org.example.test021;

public interface Travel {
    public void travel();
}

//Person.java
package org.example.test021;

public class Person {
    public Travel getTravel() {
        return travel;
    }

    public void setTravel(Travel travel) {
        this.travel = travel;
    }

    private Travel travel;

    public void travel() {
        travel.travel();
    }

}

//AirplaneTravel.java
package org.example.test021;

public class AirplaneTravel implements Travel {
    @Override
        public void travel() {
        System.out.println("乘坐飞机旅游！");
    }
}

//TrainTravel.java
package org.example.test021;

public class TrainTravel implements Travel {
    @Override
        public void travel() {
        System.out.println("乘坐火车旅游！");
    }
}

//BicycleTravel.java
package org.example.test021;

public class BicycleTravel implements Travel {
    @Override
        public void travel() {
        System.out.println("乘坐自行车旅游！");
    }
}

//Main.java
package org.example.test021;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Person person = new Person();
        Scanner sc = new Scanner(System.in);
        System.out.println("请选择你想要的旅游出行方式：1、飞机；2、火车；3、自行车");
        int i = sc.nextInt();
        if (i == 1) {
            person.setTravel(new AirplaneTravel());
        }
        else if (i == 2) {
            person.setTravel(new TrainTravel());
        }
        else if (i == 3) {
            person.setTravel(new BicycleTravel());
        }
        else {
            System.out.println("不存在这种出行方式呦~");
        }

        person.travel();
    }
}