Prevent abstract implementation from overriding certain method

Question

I have an interface called Worker which I want to expose so that the end-user can simply call:

Worker w = WorkerFactory.createInstance();
w.mainBit();

How can I prevent classes which extend my AbstractWorker class from providing their own implementation of the mainBit method?

This is the structure I have so far:

interface Worker {
    void mainBit();
}

class WorkerFactory {
    public static Worker createInstance() {
        return new WorkerImpl();
    }
}

abstract class AbstractWorker implements Worker {
    @Override
    public void mainBit() {
        this.doThing1();
        this.doThing2();
    }

    public abstract void doThing1();
    public abstract void doThing2();
}

class WorkerImpl extends AbstractWorker {
    @Override
    public void doThing1() {

    }

    @Override
    public void doThing2() {

    }

    @Override
    public void mainBit() {
        // I don't want classes to override this functionality
    }
}

Answer 1

Mark it final inside you abstract class (in Java). No other subclass will be allowed to override it.

Answer 2

Mark the method as final, which prevents overriding:

public final void mainBit()

Answer 3

If you want to always use the AbstractWorker's mainBit, make it final in this class. This way, the subclasses won't override it.

Answer 4

Use the final keyword.

public final void mainbit ()
...

Answer 5

You can do that by making the method final.