一、接口的目的

接口的目的是规范代码，在写代码之前，先通过接口规定要写哪些方法

二、定义接口

package com.guoyasoft.implement;

public interface IStudy {
    public boolean doHomeWork(String renwu);
    public int learn(String course);
}

实现接口

public class StudentCY extends Student implements IStudy{

    @Override
    public boolean doHomeWork(String renwu) {
        System.out.println("开始做作业");
        System.out.println("开始看手机");
        System.out.println("开始玩游戏");
        System.out.println("不做了");
        return false;
    }

    @Override
    public int learn(String course) {
        System.out.println("不想学");
        return 0;
    }

}

public class StudentWL extends Student implements IStudy{

    @Override
    public boolean doHomeWork(String renwu) {
        System.out.println("开始做作业");
        System.out.println("开始看手机");
        System.out.println("开始玩游戏");
        System.out.println("不做了");
        return false;
    }

    @Override
    public int learn(String course) {
        System.out.println("不想学");
        return 0;
    }

}

3. 测试

package com.guoyasoft.implement;

public class TestStudent {
    public static void main(String[] args) {

        StudentWL wl3=new StudentWL();
        wl3.doHomeWork("家庭作业");
        wl3.learn("法语");
        
        //向上转型成接口类型
        IStudy wl4=new StudentWL();
        wl4.doHomeWork("家庭作业");
        wl4.learn("法语");
    }
}