java - 强制重写类时调用基类版本方法，否则抛出异常

Question

如果重写方法没有显式调用其 super 方法，我想抛出自定义异常。如果任何类扩展类A并重写say()方法，应该强制调用super.say()来执行基类方法中编写的代码，如果失败，我想抛出自定义异常，例如super而不是异常

  class A {
    public void say() {
        System.out.println("From super");
    }
  }   

  class Demo extends A {
    @Override
    public void say() {
              //Check if user have called super.say() or not if not throw a custom  exception
       super.say();
       System.out.println("From Child");
    }

    public static void main(String[] args) {
      Demo d = new Demo();
      d.say();
    }

 }

Answer 1

这是 @DavidWallace 建议的方法，这比您想要的更好，因为它使得子类不可能阻止 say() 执行它在基类中执行的操作:

class A {
    public final void say() {
        System.out.println("From super");
        saySomethingElse();
    }

    /**
     * Subclasses can override this method to make the say() method 
     * say something else in addition to "From super".
     */
    protected void saySomethingElse() {
    }
}   

class Demo extends A {
    @Override
    protected void saySomethingElse() {
        System.out.println("From Child");
    }

    public static void main(String[] args) {
        Demo d = new Demo();
        d.say();
    }
}