This book isn't an introduction to objectoriented technology or
design. Many books already do a good job of that. This book assumes
you are reasonably proficient in at least one objectoriented
programming language, and you should have some experience in
objectoriented design as well. You definitely shouldn't have to
rush to the nearest dictionary the moment we mention "types"
and"polymorphism," or "interface" as opposed to "implementation"
inheritance.
On the other hand, this isn't an advanced technical treatise
either. It's a book of design patterns that describes simple and
elegant solutions to specific problems in objectoriented software
design. Design patterns capture solutions that have developed and
evolved over time. Hence they aren't the designs people They
reflect untold redesign and recoding as developers have struggled
for greater reuse and flexibility in their software.Design patterns
capture these solutions in a succinct and easily applied form.
The design patterns require neither unusual language features
nor amazing programming tricks with which to astound your friends
and managers. All can be implemented in standard objectoriented
languages, though they might take a little more work than ad hoc
solutions. But the extra effort invariably pays dividends in
increased flexibility and reusability.
Once you understand the design patterns and have had an "Aha!"
(and not just a "Huh?") experience with them, you won't ever think
about objectoriented design in the same way. You'll have insights
that can make your own designs more flexible, modular, reusable,
and understandable which is why you're interested in objectoriented
technology in the first place, right?
A word of warning and encouragement: Don't worry if you don't
understand this book completely on the first reading. We didn't
understand it all on the first writing! Remember that this isn't a
book to read once and put on a shelf. We hope you'll find yourself
referring to it again and again for design insights and for
inspiration.
This book has had a long gestation. It has seen four countries,
three of its authors' marriages, and the birth of two (unrelated)
offspring.Many people have had a part in its development. Special
thanks are due Bruce Andersen, Kent Beck, and Andre Weinand for
their inspiration and advice. We also thank those who reviewed
drafts of the manuscript: Roger Bielefeld, Grady Booch, Tom
Cargill, Marshall Cline, Ralph Hyre, Brian Kernighan, Thomas
Laliberty, Mark Lorenz, Arthur Riel, Doug Schmidt, Clovis Tondo,
Steve Vinoski, and Rebecca WirfsBrock. We are also grateful to the
team at AddisonWesley for their help and patience: Kate Habib,
Tiffany Moore, Lisa Raffaele, Pradeepa Siva, and John Wait. Special
thanks to Carl Kessler, Danny Sabbah, and Mark Wegman at IBM
Research for their unflagging support of this work.
Last but certainly not least, we thank everyone on the Internet
and points beyond who commented on versions of the patterns,
offered encouraging words, and told us that what we were doing was
worthwhile. These people include but are not limited to Ran
Alexander, Jon Avotins, Steve Berczuk, Julian Berdych, Matthias
Bohlen, John Brant, Allan Clarke, Paul Chisholm, Jens Coldewey,
Dave Collins, Jim Coplien, Don Dwiggins, Gabriele Elia, Doug Felt,
Brian Foote, Denis Fortin, Ward Harold, Hermann Hueni, Nayeem
Islam, Bikramjit Kalra, Paul Keefer, Thomas Kofler, Doug Lea, Dan
LaLiberte, James Long, Ann Louise Luu, Pundi Madhavan, Brian
Marick, Robert Martin, Dave McComb, Carl McConnell, Christine
Mingins, Hanspeter Mossenbock, Eric Newton, Marianne Ozcan, Roxsan
Payette, Larry Podmolik, George Radin, Sita Ramakrishnan, Russ
Ramirez, Dirk Riehle, Bryan Rosenburg, Aamod Sane, Duri Schmidt,
Robert Seidl, Xin Shu, and Bill Walker.
We don't consider this collection of design patterns complete
and static; it's more a recording of our current thoughts on
design. We welcome comments on it, whether criticisms of our
examples, references and known uses we've missed, or design
patterns we should have included. You can write us care of
AddisonWesley, or send electronic mail to
designpatterns@cs.uiuc.edu. You can also obtain softcopy
for the code in the Sample Code sections by sending the message
"send design pattern source" to
designpatternssource@cs.uiuc.edu.
Mountain View, California E.G.
Montreal, Quebec R.H.
Urbana, Illinois R.J.
Hawthorne, New York J.V.
August 1994
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