Best Patterns in 2025

The Singleton pattern ensures that only one instance of a class exists and provides a global point of access to that instance. This is crucial when precisely one object is needed to coordinate actions across a system. It's frequently used for managing database connections, thread pools, and configuration settings. While its straightforward implementation simplifies managing resources, users must understand the potential impact on testing and design flexibility. Although implementation might seem simple, the Singleton pattern can introduce tight coupling in your application because it creates a global state. Make sure this is the correct solution for you.

The Factory pattern addresses the challenge of object creation, especially when the exact type of object to be created isn't known beforehand. It provides an interface for creating objects, but lets subclasses decide which class to instantiate. This promotes loose coupling and makes the system more extensible. The Factory pattern is versatile but requires careful design considerations. Common applications include creating database connections, UI elements, and complex objects where different variations are needed.

The Composite pattern allows you to treat individual objects and compositions of objects uniformly. This is useful when you want to represent part-whole hierarchies, such as a file system or a graphical drawing composed of shapes. By using the Composite pattern, you can write code that operates on both individual objects and complex compositions without needing to know their specific structure. This simplifies the codebase and makes it easier to manage and extend. Implementers often find that it adds significant value where complex structures can be easily represented.

The Observer pattern defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically. Widely used in event-driven systems, such as user interfaces, where changes in one component trigger updates in others. The Observer pattern leads to a more flexible and maintainable system by decoupling the subject (the object being observed) from its observers. It makes it easier to add new observers and modify existing ones. Implementations can vary depending on the programming languages and specific requirements of the project, but the core concept remains consistent.

The State pattern allows an object to alter its behavior when its internal state changes. It encapsulates each state in a separate class, allowing for a flexible and maintainable design. Commonly used in complex systems, such as traffic light controllers, game characters, and order processing systems. The State pattern is useful for managing the different business process, improving readability and maintainability. Key to implementation is properly defining the states and transitions. Often the best usage is in systems with distinct states and clear transitions between them.