Re: @Override
On 7/23/2012 10:57 PM, Arne Vajh?j wrote:
On 7/23/2012 10:16 PM, Eric Sosman wrote:
On 7/23/2012 7:58 PM, Arne Vajh?j wrote:
On 7/23/2012 4:35 PM, Eric Sosman wrote:
On 7/23/2012 2:30 PM, bob smith wrote:
Is it really necessary to write @Override when you override or is this
just "a good thing"?
Two benefits of @Override appear to me, one from its presence
and one from its absence:
- If you write @Override and then misspell the method name or
mess up the parameter list, Java will say "Hey, wait: There's
nothing in the superclass with this signature; what do you
think you're doing?" And then you'll say "Oops!" and fix
the problem, instead of wondering why your "overriding" method
doesn't seem to work.
- If you write a method and your IDE starts suggesting that you
ought to tag it with @Override, you'll be alerted that you've
overridden something you didn't intend to.[*]
Two benefits; that's all I see. Hence, like indentation and
Javadoc comments, not "really necessary" ...
I see the biggest benefits being the documentation.
It can be important to know that ones method may be called
by the super class.
And all arguments seems related to extends not implements, so
I m not convinced that extending it to interface methods was
wise.
A separate @Implements annotation instead of @Override might
have been better for interfaces. But what should one do about
abstract methods in abstract superclasses? Are those @Override
or @Implements, or maybe @Concretizes? And why should the class
with the actual implementation care about the distinction? And
what about concrete methods *intended* to be overridden, as in
MouseAdapter? @ProFormaOverrides?
Looks like fodder for a "whichness of the why" debate.
I think abstract methods should be treated like other methods in
classes.
The abstract class could later introduce an implementation.
We know that the interface will never.
Ah, but what about
abstract class Super implements ActionListener {
protected void helperMethod() { ... }
... // maybe an actionPerformed() here, maybe not
}
class NowWhat extends Super {
@WhatAnnotationGoesHere // ?
public void actionPerformed(ActionEvent evt) {
...
}
}
In the NowWhat class, does actionPerformed() "implement" the
method required by the ActionListener interface, or does it
"concretize" the abstract actionPerformed() method of the Super
class? Or does it "override" Super's concrete actionPerformed()
method (not shown)? What if Super explicitly declares an abstract
actionPerformed() method?
More to the point, is the distinction useful? No, let's
"concretize" that question: Can you suggest a scenario in which
it would be helpful to distinguish among different flavors of
overriding:
- Implement a method of an interface the class `implements'
- Implement a method of a superinterface of an interface
the class `implements'
- Implement a method of an interface an abstract superclass
`implements' but leaves abstract
- Implement a method explicitly declared as abstract by an
abstract superclass
- Replace a superclass' concrete implementation
At the risk of dating myself (again), where's the beef?
--
Eric Sosman
esosman@ieee-dot-org.invalid