interface USB{
    void start();
    void stop();
}

class C{
    public static void work(USB u){
        u.start();
        System.out.println("工作中");
        u.stop();
    }
}

class USBDisk implements USB{

    @Override
    public void start() {
        System.out.println("U盘开始工作");
    }

    @Override
    public void stop() {
        System.out.println("U盘停止工作");
    }
    
}

class Printer implements USB{

    @Override
    public void start() {
        System.out.println("打印机开始工作");
    }

    @Override
    public void stop() {
        System.out.println("打印机停止工作");
    }
    
}

public class AbsDemo01 {

    public static void main(String[] args) {
        C.work(new USBDisk());
     C.work(new Printer());
    }    
}