面向接口编程的小例子

//Mosquito.java
//蚊子类，拥有一个唱歌的方法
package project.app.service;
public class Mosquito {
	public String sing() {
		return "You have to admit that I sing songs very well.";
	}
}

//Test.java
package chris;
import project.app.service.*;
public class Test {
	public static void main(String[] args) throws Exception {
		Single single = new Single();
		Mosquito mosquito = new Mosquito();
		//设置single实例和mosquito实例的关系
		single.setMosquito(mosquito);
		single.playWithMosquito();
	}
}

//Cockroach.java
//蟑螂类，有不同于蚊子的唱歌的方法
package project.app.service;
public class Cockroach {
	public String sing() {
		return "I sing when everybody is in sleep.";
	}
}

//Single.java
//单身狗类，playWithMosquito依赖于蟑螂类
package project.app.service;
import project.app.service.Cockroach;
public class Single {
	private Cockroach cockroach;
	public void setCockroach(Cockroach cockroach) {
		this.cockroach = cockroach;
	}
	public void playWithCockroach() {
		System.out.println(cockroach.sing());
	}
}

//Test.java
package chris;
import project.app.service.*;
public class Test {
	public static void main(String[] args) throws Exception {
		Single single = new Single();
		Cockroach cockroach = new Cockroach();
		single.setCockroach(cockroach);
		single.playWithCockroach();
	}
}

//Pet.java
//宠物接口，有一个唱歌的方法
package project.app.service;
public interface Pet {
	public String sing();
}

//Mosquito.java
//
package project.app.service.impl;
import project.app.service.Pet;
public class Mosquito implements Pet {
	public String sing() {
		return "You have to admit that I sing songs very well.";
	}
}

//Cockroach.java
//蟑螂类，有唱歌的方法
package project.app.service.impl;
import project.app.service.Pet;
public class Cockroach implements Pet {
	public String sing() {
		return "I sing when everybody is in sleep.";
	}
}

//Test.java
package chris;
import project.app.service.Single;
import project.app.service.Pet;
import project.app.service.impl.Cockroach;
public class Test {
	public static void main(String[] args) throws Exception {
		Single single = new Single();
		Cockroach cockroach = new Cockroach();
		single.setPet(cockroach);
		single.playWithPet();
	}
}