Design

You design and construct a system based on customer needs, or requirements. Part of the design process is translating the customer requirements into rough ideas or sketches of how the system will be used. For a web-based system, this means designing the web pages that will provide the application's functionality. If you are building "inbetween" software known as middleware, your system will be used by other client software and will interact with other server software. In this case, you will want start by defining the communication pointsthe interfacesbetween the other systems and the middleware.

You start by building only high-level designs, not highly detailed specifications. You will continually refine the design as you understand more about the customer needs. You will also update the design as you discover what works well and what doesn't work well in the Java code that you build. The power of object-oriented development can allow you this flexibility, the ability to quickly adapt your design to changing conditions.

Designing the system from the outside in as described above would be a daunting task without complete understanding of the language in which you're going to build itJava. To get started, you will construct some of the internal building blocks of the system. This approach will get you past the language basics.

The student information system is primarily about students, so as your first task you will abstract that real-world concept into its object-oriented representation. A candidate class might be Student. Student objects should contain basic information about a student such as name, identification number, and grades. You will concentrate on an even smaller concern first: Create a unique student object that stores the name of the student.

The book icon that appears to the left of the preceding paragraph will appear throughout Agile Java. I will use this icon to designate requirements, or stories, that you will build into the student information system. These stories are simple descriptions of what you need to build into the system in order to make the customer happy. You will translate stories into detailed specifications that you realize in the form of tests.