The document discusses several software design patterns:
1. The Observer pattern allows a subject to notify multiple observers of any state changes. This is used for RSS feeds and news servers to automatically update clients.
2. The Factory pattern helps create object instances at runtime depending on conditions. This is used to create random shapes in a painting program or load database tables on demand.
3. The Singleton pattern ensures only one instance of a non-sharable resource exists. This is used for database connections, base classes, and other shared resources.
4. Design patterns help development by promoting good object-oriented design, reusability, communication through a shared vocabulary, and faster development times.
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