Tutorial: Keeping Your Java Objects Informed with the Observer Design Pattern:

Keeping Your Java Objects Informed with the Observer Design Pattern

by Barry Burd and Michael P. Redlich

This article, the second in a series on design patterns, introduces the Observer pattern, one of the 23 design patterns defined in the legendary 1995 book Design Patterns—Elements of Reusable Object-Oriented Software. The authors of this book, Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, are known affectionately as the "Gang of Four." (So popular is this book that the Gang of Four has its own acronym—GoF.)

Design Patterns

• A creational pattern abstracts the instantiation process.
• A structural pattern groups objects into larger structures.
• A behavioral pattern defines better communication among objects.

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