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Orpheo
Orpheo

Reputation: 406

how to avoid using a empty method implementation?

I have a question regarding the structures of my classes in java :

I have a first class : MyClass that is abstract

public abstract class MyClass
{
    protected void abstract monitor();
}

then I have an abstract iterator on it 

public abstract class MyClassIterator<T> extends MyClass
{
    protected void abstract monitor(T data);
}

In practice I will after create classes that will either inherit from MyClass or MyClassIterator.

I want to make sure all instances of MyClass implement monitor but for the iterator ones, how can I avoid inserting something like 

protected void monitor() {};

just to implement it :/

Thanks for any idea :)

Upvotes: 1

Views: 2582

Answers (2)

Ron C
Ron C

Reputation: 1206

If you don't want that MyClassIterator subclasses will have to implement this method, then you have to add the empty implementation to MyClassIterator. You can also throw some exception in the implementation.

public abstract class MyClassIterator<T> extends MyClass
{
    protected abstract void monitor(T data);

    protected void monitor() {
        //optional
        throw new UnsupportedOperationException();
    }
}

Note: You can't write void before abstract, you need to fix this in your monitor(T data) method, like in my answer.

Upvotes: 1

ToYonos
ToYonos

Reputation: 16833

Add a default implementation of monitor in MyClass, with a customized exception

public abstract class MyClass
{
    protected void abstract monitor()
    {
        throw new NotImplementedException();
    }
}

Thereby, MyClassIterator won't have to implement the method and other subclasses of MyClass will have to override it.

Upvotes: 3

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