Overriding

[prasanna1157]

Hello All,
Why is that a subclass method that is overriding a base class method can't be more restrictive?

That is, why can't the access specifier be protected/private when the base class method is public?

Please explain with examples.

What is the primary reason behind disallowing this?


Thanks,
Prasanna

[masijade]

Because the developers of the language wanted it that way. Also, the developer of a class that creates a method that is to be public wants it to remain public even in subclasses. Also, extending a class means the sub class is, also, a valid instance of the super type, but if one of the methods is now more restricted than it was for the super type, that subclass would no longer be a valid instance of that supertype.

Now, I hope this answers your homework question well enough. An example you can come up with for yourself.

[prasanna1157]

Thank You.

But, what would happen if it were allowed?

Could you illustrate?

This is not a homework question!! It is something that I was just pondering. That's why I asked for an example, as I couldn't think of what would happen when something like that is allowed!!


Thanks,
Prasanna

[Prajin]

But, what would happen if it were allowed?

Didn't masijade said

but if one of the methods is now more restricted than it was for the super type, that subclass would no longer be a valid instance of that supertype.

-Regards

[masijade]

Could you illustrate?

No. Besides I see you've had this question, and more, answered in your cross-post on Sun and that cross-post contains a reference to another cross-post, as well.

[prasanna1157]

Oh, that's fine.

Yes, I did post there as well.

Since I wasn't clear initially even after getting a reply there, I thought I needed another example. That's why I posted.

I did it just because I did not understand it at the time of posting. I don't know why that would be a problem.


Thanks,
Prasanna

[DarrylBurke]

The other cross post
Method Overriding (Java in General forum at JavaRanch)

db

[DarrylBurke]

Since I wasn't clear initially even after getting a reply there, I thought I needed another example. That's why I posted.

You said the same thing on the Sun/Oracle forums.

db