Re: Set and .equals() semantics

"Mark Space" <markspace@sbc.global.net> wrote in message
news:U4JUj.2702$3O7.1685@newssvr19.news.prodigy.net...


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.