[jdom-interest] Re: List's in JDOM - a small essay

Patrick Dowler patrick.dowler at nrc.ca
Fri Mar 9 13:44:53 PST 2001

On 09 March 2001 11:30, Joseph Bowbeer wrote:
> I'm interested in comparing the singly linked design with the design I
> sketched in a previous message, which is a sequential list implementation
> based on a reversible, mutable FilterListIterator and using an ArrayList or
> a LinkedList as the underlying representation.

FilterIterator-type semantics are very convenient and powerful, aside from
having any FIlterList at all. One could simple get an Iterator from the
element's LinkedList and wrap a FilterIterator around it.

> Using an ArrayList as the underlying representation is very lean in terms
> of memory usage and very performant for a large set of uses.  A filtered
> version of this would have the performance characteristics of a
> doubly-linked list, with no significant additional memory overhead.

Until you try to insert near the front of a large list :-( 

Having said that, some uses favour ArrayList and others favour LinkedList.
The fact that both exist is testament to the fact that neither is best in all 

Uses of doubly-linked/reverse traversal:

- applications which allow for interactive editting of content: in an 
   editor, do you use up-arrow or down-arrow more?

- applications which look for structural patterns: ie. how would this impact 
  XPath design/implementation?

I think tailoring JDOM for forward traversal is good for people doing 
server-side web (ie. streaming) apps, but maybe not for everyone.

Patrick Dowler
Canadian Astronomy Data Centre
National Research Council
Victoria, BC

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