[jsword-devel] Java conundrum

[Martin Denham]

Hi DM,

There are specific contains() implementations in VerseRange.
    public boolean contains(Verse that) {
        return v11n.distance(start, that) >= 0 && v11n.distance(that, end)
>= 0;
    }

    public boolean contains(Key key) {
        if (key instanceof VerseRange) {
            return contains((VerseRange) key);
        }
        return false;
    }

The second is being called but returns false because key is not a
VerseRange. If the implementation of VerseRange.contains(Key) is the
problem then another clause added at the end of the method might be one way
to fix it, like:
    public boolean contains(Key key) {
        if (key instanceof VerseRange) {
            return contains((VerseRange) key);
        }
        if (key instanceof Verse) {
            return contains((Verse) key);
        }
        return false;
    }

Martin


On 7 May 2013 14:12, DM Smith <dmsmith at crosswire.org> wrote:

> Sorry for not replying earlier. Have been on holiday.
>
> This conundrum should bee seen as a bug. Both should return the same value.
>
> I have an idea of what is happening (I have a masters degree in computer
> science for compiler construction), but until I trace it I won't be sure. I
> think that it is compile time determination of what is being called.
>
> In the gen_all case, it is known that it is a VerseRange and that
> VerseRange has a more specific contains(Verse). So that is called.
>
> In the gen_allKey case, it is no longer a VerseRange but a Key (which
> should not know anything about a Verse, since it is supposed to work for
> all kinds of Keys). So it cannot call contains(Verse) but only
> contains(Key).
>
> I'll see what I can find out.
>
> -- DM
>
> On May 4, 2013, at 5:34 AM, Martin Denham <mjdenham at gmail.com> wrote:
>
> > Here is an interesting problem (based on VerseRangeTest.java):
> >
> >     private VerseRange gen_all = ...;
> >
> >     public void testKeyContainsVerse() {
> >         // this passes
> >         assertTrue(gen_all.contains(gen11));
> >
> >         // this fails
> >         Key gen_allKey = gen_all;
> >         assertTrue(gen_allKey.contains(gen11));
> >     }
> >
> > This caught me out for a while.  I think the second assert should pass
> but Key is an interface with a single non-overloaded contains():
> >     boolean contains(Key key);
> >
> > Whereas VerseRange contains overloaded methods like contains(Verse) that
> are not called because the Key interface is being used.  At least that is
> what I think is happening.
> >
> > Is this a bug?
> >
> > Martin
> >
> >
> >
> >
> > _______________________________________________
> > jsword-devel mailing list
> > jsword-devel at crosswire.org
> > http://www.crosswire.org/mailman/listinfo/jsword-devel
>
>
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>
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