OnJava8-Examples/reuse/Wind.java

// reuse/Wind.java
// <20>2016 MindView LLC: see Copyright.txt
// Inheritance & upcasting.

class Instrument {
  public void play() {}
  static void tune(Instrument i) {
    // ...
    i.play();
  }
}

// Wind objects are instruments
// because they have the same interface:
public class Wind extends Instrument {
  public static void main(String[] args) {
    Wind flute = new Wind();
    Instrument.tune(flute); // Upcasting
  }
}
/* Output: (None) */