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Introduction to "Design Techniques"

A look at the role of design in the context of the overall software development process

By Bill Venners, JavaWorld.com, 02/01/98

At last year's JavaOne conference, I attended a session in which the speaker talked about Sun's plan for the Java virtual machine (JVM). In this talk, the speaker stated that Sun planned, among other things, to clear up current performance bottlenecks in its virtual machine, such as the slowness of synchronized methods and the performance costs of garbage collection. The speaker stated Sun's goal: With the improvements to the JVM, programmers would not need to think about avoiding virtual machine bottlenecks when they designed their programs; they would only need to think of creating "good object-oriented, thread-safe designs."

The speaker did not, however, elaborate on what actually constitutes a good object-oriented, thread-safe design. That is the aim of this new column. Through the articles of the Design Techniques column, I hope to answer the question: What is a good Java program design, and how do you create one?

The column's focus

My focus in this column will be to provide practical design techniques that you can put to use in your everyday programming tasks. I'll assume you are familiar with the Java language and APIs. I plan to discuss techniques, ideas, and guidelines that will help you use the language and APIs in your real-world programs.

To give you an idea of what to expect in this column, here is a list of the kinds of topics I plan to write about:

• Ways to improve the design of your objects
• Building class hierarchies
• What are interfaces for?
• What is the point of polymorphism?
• Choosing between composition and inheritance
• Designing for thread safety
• Designing for thread cooperation
• The Model/Controller/View architecture used by the JFC classes
• Design patterns

Much of the material that has already been written about software design can be applied to Java. There are many full-featured design methodologies and thick textbooks that describe them. In this column I won't promote one methodology over another. Nor will I promote a new methodology of my own invention. Rather, I will draw on and combine insights that I've gained from several existing methodologies and found to be useful in my own programming practice.

The approach to design that I will recommend in these articles arises out of my experiences over the years in the cubicle: designing new software, enhancing old software, maintaining software written by others, maintaining software written by myself, working with various languages, tools, computers, and other programmable machines. My design philosophy will be very "cubicle-oriented": based on, and geared toward, real-world commercial programming.

This month: Process described, "design" defined

In this initial article of the Design Techniques column, I will provide a detailed account of the concept of software design based on my own experience as a developer. In the remainder of this article, I'll discuss the process of software development and explain what I mean by the term "design."

The software development process

In my experience, the process of software development tends to be rather chaotic. Team members come and go, requirements change, schedules change, entire projects get canceled, entire companies go out of business, and so on. The programmer's job is to successfully navigate this chaos and in the end produce a "quality" product in a "timely" manner.

 

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