Design patterns are reusable solutions to common problems that software developers face in designing applications. A design pattern provides a general template that can be adapted to a specific problem, thus facilitating software development and enhancing code quality.
Design patterns are divided into three categories: creational, structural, and behavioral patterns.
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Creational patterns deal with object creation mechanisms, trying to create objects in a manner suitable for the situation. Examples of creational patterns include the Singleton pattern, Factory pattern, Abstract Factory pattern, and Builder pattern.
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Structural patterns deal with object composition and provide ways to compose objects to obtain new functionalities. Examples of structural patterns include the Adapter pattern, Bridge pattern, Decorator pattern, and Facade pattern.
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Behavioral patterns deal with communication between objects, and describe the patterns of communication between objects in a system. Examples of behavioral patterns include the Observer pattern, Command pattern, Strategy pattern, and Template Method pattern.
Design patterns help in building software that is more flexible, reusable, and maintainable. They provide a common vocabulary for developers, and can also help in communicating solutions to others in a clear and concise manner. Moreover, by using well-established design patterns, developers can save time by not having to re-invent the wheel and can focus on other aspects of the software development process, such as testing and deployment.