Re: iterators

From:

Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 04 Aug 2009 20:09:27 -0700

Message-ID:

<PJ6em.110850$vp.56394@newsfe12.iad>

Stefan Ram wrote:

ram@zedat.fu-berlin.de (Stefan Ram) writes:

class Example
implements de.dclj.ram.Value<T>, de.dclj.ram.Advanceable
{ public T value(){ ... }
public boolean advance(){ ... }}

  I made a design error:

  If there is not even one first value available,
  the client can not detect this. So now, I prefer:

class ExampleIterator
implements
de.dclj.ram.IsAvailable,
de.dclj.ram.Value<T>,
de.dclj.ram.Advanceable,
{ public boolean IsAvailable(){ ... }
  public T value() { ... }
  public void advance() { ... }}

It gets more complicated than that if you consider different classes of
iterators (ListIterators in Java for example, or Random Access Iterators
in C++)

ListIterators actually keep track of the location "between" elements.
isAvailable doesn't make sense in that case.

One thing that I miss in Java is reversible iterators. Actually, there
are a lot of things I'd like to rework in the Java collections library,
but unfortunately there aren't any ways of doing so without breaking
everything or creating ugly bridge code.

What I would *love* is an iterator that can be made smart enough to not
throw ConcurrentModificationException if the modification can be proven
to be non-conflicting (such as appending to a list, or removing a node
from a linked-list, which is not any node being pointed to by the iterator.)

--
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