Extending an Interface with Inheritance

最新推荐文章于 2022-01-14 10:04:07 发布

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本文通过《OnJava8》中的示例代码，展示了Java中接口如何通过继承实现多接口的功能组合，包括Monster、DangerousMonster、Lethal和Vampire等接口的定义与实现。

// interfaces/HorrorShow.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Extending an interface with inheritance

interface Monster {
  void menace();
}

interface DangerousMonster extends Monster {
  void destroy();
}

interface Lethal {
  void kill();
}

class DragonZilla implements DangerousMonster {
  @Override
  public void menace() {}

  @Override
  public void destroy() {}
}

interface Vampire extends DangerousMonster, Lethal { // note here.
  void drinkBlood();
}

class VeryBadVampire implements Vampire {
  @Override
  public void menace() {}

  @Override
  public void destroy() {}

  @Override
  public void kill() {}

  @Override
  public void drinkBlood() {}
}

public class HorrorShow {
  static void u(Monster b) {
    b.menace();
  }

  static void v(DangerousMonster d) {
    d.menace();
    d.destroy();
  }

  static void w(Lethal l) {
    l.kill();
  }

  public static void main(String[] args) {
    DangerousMonster barney = new DragonZilla();
    u(barney);
    v(barney);
    Vampire vlad = new VeryBadVampire();
    u(vlad);
    v(vlad);
    w(vlad);
  }
}

The syntax used in Vampire works only when inheriting interfaces. Normally, you can use extends with only a single class, but extends can refer to multiple base interfaces when building a new interface. Notice that interface names are separated with commas.

references:

1. On Java 8 - Bruce Eckel

2. https://github.com/wangbingfeng/OnJava8-Examples/blob/master/interfaces/HorrorShow.java