Re: iterating the difference of two collections

John Ersatznom <j.ersatz@nowhere.invalid>
Mon, 08 Jan 2007 04:41:56 -0500
Mike Schilling wrote:

"Andreas Leitgeb" <> wrote in message

Mike Schilling <> wrote:

   public class Subset extends AbstractSet implements Set {

Btw., is there a reason for "implements Set", when AbstractSet
already does it?


The class name contains "set". It extends a class whose name contains
"Set". "All implemented interfaces" will include "Set". What more
documentation do you want? ;)

The really interesting thing here is whether to make Subset modifiable.
One supposes removal should remove the element from the backing Set, and
addition should add to the backing Set and throw something if the
criterion is violated (the new element would not actually now appear in
the Subset). Anyone who wants an unmodifiable one has
Collections.unmodifiableSet available to them, and anyone who wants a
Subset to diverge from its parent Set and just initially contain the
appropriate Subset, then be modifiable at will (and not reflect changes
in the backing Set), can use Set foo = new HashSet();
foo.addAll(mySubset); to copy the Subset into a normal-behaving HashSet.

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