JavaSE-12.1.3【接口名作为形参和返回值】

package day3.yub4by01.p3;

/*
1.3 接口名作为形参和返回值

    方法的形参是接口名，其实需要的是该接口的实现类对象
    方法的返回值是接口名，其实返回的是该接口的实现类对象

 */

public class JumppingDemo {

    public static void main(String[] args) {
        JumppingOperator jo = new JumppingOperator();
        Jumpping j = new Cat();
        jo.useJumpping(j);

        Jumpping j2 = jo.getJumpping(); //new Cat();
        j2.jump();
    }

}

　　

package day3.yub4by01.p3;

public class JumppingOperator {

    public void useJumpping(Jumpping j){ //多态Jumpping j = new Cat();
        j.jump();
    }

    public Jumpping getJumpping(){
        Jumpping j = new Cat();
        return j;
    }

}

　　

package day3.yub4by01.p3;

public interface Jumpping {

    void jump();

}

　　

package day3.yub4by01.p3;

public class Cat implements Jumpping{
    @Override
    public void jump() {
        System.out.println("猫猫会跳高吗");
    }
}