music2.java

来自「《Java编程思想》第四版源代码」· Java 代码 · 共 41 行

//: polymorphism/music/Music2.java
// Overloading instead of upcasting.
package polymorphism.music;
import static net.mindview.util.Print.*;

class Stringed extends Instrument {
  public void play(Note n) {
    print("Stringed.play() " + n);
  }
}

class Brass extends Instrument {
  public void play(Note n) {
    print("Brass.play() " + n);
  }
}

public class Music2 {
  public static void tune(Wind i) {
    i.play(Note.MIDDLE_C);
  }
  public static void tune(Stringed i) {
    i.play(Note.MIDDLE_C);
  }
  public static void tune(Brass i) {
    i.play(Note.MIDDLE_C);
  }
  public static void main(String[] args) {
    Wind flute = new Wind();
    Stringed violin = new Stringed();
    Brass frenchHorn = new Brass();
    tune(flute); // No upcasting
    tune(violin);
    tune(frenchHorn);
  }
} /* Output:
Wind.play() MIDDLE_C
Stringed.play() MIDDLE_C
Brass.play() MIDDLE_C
*///:~