Summary

Bruce Eckel's Thinking in Java Contents | Prev | Next

Coming up with a design such as TrashVisitor.java that contains a larger amount of code than the earlier designs can seem at first to be counterproductive. It pays to notice what you’re trying to accomplish with various designs. Design patterns in general strive to separate the things that change from the things that stay the same . The “things that change” can refer to many different kinds of changes. Perhaps the change occurs because the program is placed into a new environment or because something in the current environment changes (this could be: “The user wants to add a new shape to the diagram currently on the screen”). Or, as in this case, the change could be the evolution of the code body. While previous versions of the trash-sorting example emphasized the addition of new types of Trash to the system, TrashVisitor.java allows you to easily add new functionality without disturbing the Trash hierarchy. There’s more code in TrashVisitor.java, but adding new functionality to Visitor is cheap. If this is something that happens a lot, then it’s worth the extra effort and code to make it happen more easily.



Comments

  • There are no comments yet. Be the first to comment!

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Complex hybrid environments can make it difficult to track interdependencies, increasing the risk of disrupting critical business services. In this white paper by EMA, you'll learn how application discovery and dependency mapping can help you: Meet granular targets for availability, cost, and time-to-revenue for cloud services. Accelerate mean time to repair (MTTR) while communicating better with stakeholders. Manage even the most complex hybrid environments more efficiently and effectively Understand the …

  • Rocket Mobile® for IBM i is an enterprise mobile application development and deployment platform for customers who rely on the IBM i system. Rocket Mobile for IBM i enables customers to leave proven applications in-place and rapidly repurpose them into new managed and secure mobile applications. Fast, easy creation of mobile, web, and hybrid mobile applications that deploy to any iOS, Android, or Windows mobile phone or tablet Built-in integration for seamless repurposing of existing IBM i applications …

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date