8.1向上转型

package sedion.nsg.upcasting;
 
public enum Note {
    MIDDLE_C,C_SHARP,B_FLAT;
}

　　
package sedion.nsg.upcasting;
public class Instrument {
    public void play(Note n){
        Syso.print("Instrument.play()");
    }
}

　　
package sedion.nsg.upcasting;
 
public class Wind extends Instrument{
    public void play(Note n){
        Syso.print("Wind.play()");
    }
}

　　
package sedion.nsg.upcasting;
 
public class Music {
    public static void tune (Instrument i){
        i.play(Note.MIDDLE_C);
    }
    public static void main(String[] args) {
        Wind flute = new Wind();
        tune(flute);
    }
}