Search code examples
javapolymorphismsuper

How do I force a polymorphic call to the super method?


I have an init method that is used and overridden through out an extensive heirarchy. Each init call however extends on the work that the previous did. So naturally, I would:

@Override public void init() {
   super.init();
}

And naturally this would ensure that everything is called and instantiated. What I'm wondering is: Can I create a way to ensure that the super method was called? If all of the init's are not call, there is a break down in the obejct, so I want to throw an exception or an error if somebody forgets to call super.

TYFT ~Aedon


Solution

  • Here's one way to raise an exception if a derived class fails to call up to the superclass:

    public class Base {
        private boolean called;
        public Base() { // Doesn't have to be the c'tor; works elsewhere as well.
                        // In fact, shouldn't call overridable methods from c'tor.
            called = false;
            init();
            if (!called) {
                // throw an exception
            }
        }
        protected void init() {
            called = true;
            // other stuff
        }
    }