Re: [PATCH] Field position attribute handling

[Dalibor Topic]

Mark Wielaard wrote:
> Hi,
>
> On Wed, 2003-11-19 at 02:14, Dalibor Topic wrote:
>
> > > The documentation and code don't match up now.
> > > My Class Library book seems to indicate that it actually is instanceof,
> > > thought in most cases your code comparing the actual Class seems more
> > > correct.
> >
> > It's the recommended way of doing equals() if you want to avoid symmetry
> > bugs. See PRAXIS 12 in Peter Haggar's Practical Java, or §5.1, p 119 in
> > Java 2 performance and idion guide by craig lahrmann & rhett guthrie, or
> > Effective Java by Joshua Bloch. Using instanceof is a bad idea because
> > it allows for symmetry bugs:
>
>
> I know. But that wasn't the point. If you change to code then you must
> also update the documentation.

O.K., I just wans;t very sure about a non-ambigous wording. How about 
the attached patch?

2003-11-23  Dalibor Topic <address@hidden>

        * java/text/FieldPosition.java (equals): Fixed comment.

> > The rest follows recommendations from Joshua Bloch on writing good 
> > hashCode methods.
>
>
> It would be nice if we had something about the right way (tm) of writing
> the standard clone(), toString(), hashCode() and equals() in the Hackers
> Guide. (hint...)

I see. I'll try to come up with something based on what I've seen on the 
web and Bloch's book.

> > If two objects are not equal, they should have different hashCodes. 
> > field_attribute is checked in the equality test, so it should play a 
> > role in hashCode calculation as well.
>
>
> Should yes, but not must. I was just wondering whether or not the
> field_attribute really matters since that field and field_id indicate
> the same property. Having cheap hashCode() methods is a good thing and
> IMHO field_attribute does not make the hashCode() more specific. But if
> you think otherwise then please do it as you have it now.

True. I'll write some test code, and may post another patch that removes 
it based on what I find.

cheers,
dalibor topic

Index: java/text/FieldPosition.java
===================================================================
RCS file: /cvsroot/classpath/classpath/java/text/FieldPosition.java,v
retrieving revision 1.6
diff -u -r1.6 FieldPosition.java
--- java/text/FieldPosition.java        19 Nov 2003 17:41:21 -0000      1.6
+++ java/text/FieldPosition.java        23 Nov 2003 20:34:53 -0000
@@ -168,7 +168,7 @@
    * <p>
    * <ul>
    * <li>The specified object is not <code>null</code>.
-   * <li>The specified object is an instance of <code>FieldPosition</code>.
+   * <li>The specified object has the same class as this object.
    * <li>The specified object has the same field identifier, field attribute 
    * and beginning and ending index as this object.
    * </ul>