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Java™ Design Patterns: A Tutorial
book

Java™ Design Patterns: A Tutorial

by James W. Cooper
February 2000
Intermediate to advanced
352 pages
6h 31m
English
Addison-Wesley Professional
Content preview from Java™ Design Patterns: A Tutorial

Chapter 26. The Visitor Pattern

The Visitor pattern turns the tables on our OO model and creates an external class to act on data in other classes. This is useful when you have a polymorphic operation that cannot reside in the class hierarchy for some reason. For example, the operation wasn't considered when the hierarchy was designed or because it would clutter the interface of the classes unnecessarily.

Motivation

While at first it might seem "unclean" to put operations that should be inside of a class in another class instead, there are good reasons for doing this. Suppose that each of a number of drawing object classes has similar code for drawing itself. The drawing methods might differ, but they probably all use underlying utility functions ...

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Publisher Resources

ISBN: 0201485397Purchase book