20 arguments of String / 1 argument of String[]

maybe.

Arne

Firstly, why does it not seem right to you to perform this operation in the
constructor?

Constructor are generally used to establish a minimum safe state of an
object, before which this object cannot be reliably depended upon.

If your object is useless (or perhaps dangerous) before all its 20+ class
variables are created, then parsing your string in the constructor seems
right to me: you are providing the shortest possible time between creating
the object and having it serve a useful purpose, thus minimising the time
during which a drunken, "Half-instantiated," object could cause problems
for its poor neighbours.

I don't think any of the GOF patterns were codified as a solution to this
problem (there is an unlimited number of problems that the GOF patterns
don't address).

The only alternative I can think necessarily begins with the assumption that
your object can play a useful role without all its 20+ variables created
(which I don't think is the case here), particularly if later interactions
with the object could alter either the nature of the 20+ variables to be
created, or the behaviour of the object itself.

This sort-of sounds like an Antipattern called 'Accumulate and Fire'
based on the description.

You should not use factory unless different behavior for the same
interface is desired. Can you provide more information about the
problem this class is trying to solve?

-cheers,
Manish