[jdom-interest] Announce: JDOMPlus a flexible XML framework f or Java

James Strachan james at metastuff.com
Wed Dec 6 04:41:27 PST 2000

----- Original Message -----
From: "Jason Hunter" <jhunter at collab.net>
> I don't agree.  I think read-only trees have their place.  However, I
> lean toward having them implemented the same way Collections do, with
> facade classes.

Just being a pedant for a moment. Are you sure Collections use facade

To quote from http://rampages.onramp.net/~huston/dp/facade.html

"Facade ... provide a unified interface to a set of interfaces in a
subsystem. Facade defines a higher-level interface that makes the subsystem
easier to use."

"Facade defines a new interface, whereas Adapter uses an old interface.
Remember that Adapter makes two existing interfaces work together as opposed
to defining an entirely new one. [GOF, p219]"

(I don't have GOF to hand so am trusting this site for its facade

Java 2 Collections implement read only collections via alternate
implementations of the collections interfaces. There are singleton immutable


Each of these use private implementations of List, Map and Set which fully
implement their respective interfaces, they just throw
UnsupportedOperationException when someone attempts to change their value.

Also I could define my own read only List via

public FooList extends AbstractList {

and make it readonly via a similar mechanism.

Neither of these mechansims use different interfaces, they are just
implement the regular collection interfaces - so they aren't facades are


James Strachan
email: james at metastuff.com
web: http://www.metastuff.com

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