[求助]请教，可以编译但不能运行【已解决】

//: polymorphism/music/Note.java
// Notes to play on musical instruments.
package polymorphism.music;

public enum Note {
MIDDLE_C, C_SHARP, B_FLAT; // Etc.
}

//: polymorphism/music/Instrument.java
package polymorphism.music;
import static net.gondi.util.Print.*;

class Instrument {
public void play(Note n) {
print("Insturment.play()");
}
}

//: polymorrphism/music/Wind.java
package polymorphism.music;

// Wind objects are instruments
// because they have the same interface:
public class Wind extends Instrument {
// Redefine interface method:
public void play(Note n) {
System.out.println("Wind.play() " + n);
}
}

//: polymorphism/music/Music.java
// Inheritance & upcasting.
package polymorphism.music;

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); // Upcasting
}
}