Re: Finding nearest location, calculating distance - best way to store and sort info?

the custom comparator is interesting. however, the distance from my
central point should only be calculated once for each object. will it
be calculated every time two objects are compared? in other words,
many, many times when ordering a list.

thanks,
matt

On 5/3/06, Arturo Perez <[email protected]> wrote:
> Matt Kime wrote:
> > I have a database of addresses and i'm trying to find the nearest
> > locations. Rather than computing the distance for all the addresses in
> > the database, I'm starting by creating an array of addresses within x
> > distance. Now that I have my array, I'm finding myself at my limit of
> > java knowledge. I'd like to create an associative array that i can
> > sort with, storing objects and sorting on their distance. What is the
> > best java tool for this? The different types of maps are confusing me
> > and I'm not sure if they'll work for what i want anyway. (it seems
> > that a sortedMap won't work if I want to store an object - no way to
> > compare my address objects)
> >
> > what solutions have you employed?
>
> When I've had to do this I used the database to calculate and return the
> addresses in sorted order using a city-block metric.
>
> Say you have the addresses with lat/long info.  You want the addresses
> within 5 miles of a given address.  The SQL (yeah, I know, evil) would
> be something like
>
>     SELECT address from ADDRESS where address.x between ($1.x and $1.x +
> 5) and address.y between ($1.y and $1.y + 5).
>
> If you want to do it in Java then you can put everything into an array
> and write a custom Comparator to do the calculation for you:
>     Collections.sort(array, new Comparator() { ...distance calculation });
>
> Are these enough of hints?
> -arturo
>