Chapter 1 - Introduction to Software Patterns Patterns in Java, Volume 1: A Catalog of Reusable Design Patterns Illustrated with UML, Second Edition by Mark Grand John Wiley & Sons � 2002

Chapter 1: Introduction to Software Patterns

Overview

Software patterns are reusable solutions to recurring problems that we encounter during software development. Because this book is all about software patterns, they are simply referred to as patterns throughout.

What makes a bright, experienced programmer much more productive than a bright, but inexperienced programmer? Experience. Experience gives programmers a wealth of wisdom. As programmers gain experience, they recognize the similarity of new problems to those they have solved in the past. With even more experience, they recognize that solutions to similar problems follow recurring patterns. With knowledge of these patterns, experienced programmers can recognize a problem to which specific patterns apply and immediately determine the solution without having to stop to analyze the problem first.

When a programmer discovers a pattern, it’s just an insight. In most cases, to go from an unverbalized insight to a well-thought-out idea that the programmer can clearly articulate is surprisingly difficult. It’s also an extremely valuable step. When we understand a pattern well enough to put it into words, we are able to intelligently combine it with other patterns. More important, once put into words, a pattern can be used in discussions among programmers who know the pattern. Such discussions allow programmers to more effectively collaborate and combine their wisdom. They can also help avoid the situation in which programmers argue over different solutions to a problem but find that they were actually thinking of the same solution, only expressing it in different ways.

Putting a pattern into words has an additional benefit for less experienced programmers who have not yet discovered the pattern. Once a pattern has been put into words, more experienced programmers can teach it to programmers who aren’t familiar with the pattern.

The intended value of this book is that it provide experienced programmers with a common vocabulary to discuss patterns. It should also allow programmers who have not yet discovered a pattern to learn about the pattern.

Although this book includes a substantial breadth of patterns, you may discover additional patterns yourself. Some patterns that you discover may be highly specialized and of interest only to a small number of people. Other patterns may be of broad interest and worthy of inclusion in a future volume of this book. If you wish to communicate such a pattern to this book’s author, you may send an email to mgrand@mindspring.com.

The patterns cataloged in this book convey constructive ways for organizing parts of the software development cycle. There are, however, nonconstructive patterns that can recur in programs. These are called AntiPatterns because they can cancel out the benefits of patterns. This book does not attempt to catalog AntiPatterns, for the subject is well covered in other books.

Patterns and AntiPatterns are similar but fundamentally different. The point of a pattern is to recognize when you have the opportunity to apply a good solution to a problem. The point of an AntiPattern is to recognize the nature of a bad situation and suggest solutions.