Re: Set and .equals() semantics
"Mark Space" <markspace@sbc.global.net> wrote in message
news:U4JUj.2702$3O7.1685@newssvr19.news.prodigy.net...
Rex Mottram wrote:
which can both look up and retrieve a reference. But I hope I'm
misunderstanding something which would allow me to use the more natural
Set design.
Nope, I think I agree. Set and subclasses could benefit from a "find()"
method which does an equals() or hashcode() lookup as appropriate and
returns the element already in the set.
That is, every set should build a hash table of its contents whether it
needs one or not? I disagree. (Though it would be trivial to add find()
specifically to HashSet, which is implemented on top of HashMap.)
What could be useful is an adapter class to provide find() to a Set,
something like
public class LookupSet<T> implements Set<T>
{
private Set<T> underlyingSet;
private Map<T , T> map;
public LookupSet<T>(Set<T> underlyingSet)
{
this.underlyingSet = underlyingSet;
map = new HashMap<T, T>();
}
public T find(T key)
{
return map.get(key);
}
// Forward all Set calls, modifying the map as need be
}
Not that this is hard to build yourself.
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