[jsword-devel] Java conundrum

DM Smith dmsmith at crosswire.org
Tue May 7 06:12:29 MST 2013

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
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