When would you use Final with Protected?

[stormbind]

From what I think I can see, javax.swing.text.DefaultStyledDocument inherits two methods:

final protected writeLock()
final protected writeUnlock()

I would like to make use of these methods. I cannot call them from another class because they are protected, and I cannot override them because they are final.

When would you use the same combination of final and protected?

I am also curious to know how one can gain control of the writeLock

--Glen

Memoria mihi benigna erit qui eam perscribam

 

[Diancecht]

protected final means subclasses can call it but not modify, ie, call it "as is".

Cheers,
Dian

 

[stormbind]

I did realise this after posting (-:

Isn't it very anti-OOP to force uses "as is" and also very anti-iterative development processes?

Now my original post is redundant, but for arguments sake, lets assume one of us really did want to override that method in that class... how far up the tree would we need to go and how many classes would we need to replace?

--Glen

Memoria mihi benigna erit qui eam perscribam

 

[Diancecht]

You can't override that, if you actually need to replace that method, you should use another one with another name.

There are a lot of uses for final keyword totally OOP. For example, String class is final.

Here you have some more uses:

http://java.sun.com/docs/books/tutorial/java/IandI/final.html

http://renaud.waldura.com/doc/java/final-keyword.shtml#methods

Cheers,
Dian

 

[cpjust]

Then use composition instead of inheritence.

I think if you use final protected (public, private, whatever) it allows the compiler to make certain optimizations that it wouldn't be able to make otherwise.

 

[Diancecht]

Only JIT compilers can take some advantage of final methods, I don't think it's a good idea to use final for perfomance reasons.

Btw, private methods cannot be overriden and they're a good OO practice.

Cheers,
Dian

 

[stormbind]

> You can't override that, if you actually need to replace
> that method, you should use another one with another
> name.

Other inherited methods will call the originally named method, so wouldn't you end up replacing many methods?

--Glen

Memoria mihi benigna erit qui eam perscribam

 

[Diancecht]

It it's final and protected, that means the original developer wanted to be sure that all the methods called the original one.

The OOP power is not only in what you show but also in what you hide.

Imagine for example a Java program for parental control. If you have a method control where age check is performed, you don't want that method to be overriden, changed or extended in any way, and you don't want other class to call any other method but the one you implemented.

Cheers,
Dian

 

[stormbind]

I feel there is a difference in an application and an API. I would like the API to empower me. So we can agree to disagree

--Glen

Memoria mihi benigna erit qui eam perscribam