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Programming Concepts Intermediate

What is Singleton Pattern?

A design pattern that restricts a class to a single instance and provides a global point of access to that instance.

The Singleton pattern ensures only one instance of a class exists throughout the application lifetime. It provides a global access point via a static method (e.g., getInstance()). The constructor is made private to prevent direct instantiation.

Common uses include database connections, logging, configuration management, and thread pools. Critics argue singletons introduce global state and make testing harder. Dependency injection is often preferred as an alternative.

Related Terms

Twelve-Factor App
A methodology of twelve best practices for building modern, scalable, maintainable software-as-a-service applications.
Debugging
The process of finding and fixing errors (bugs) in software code to ensure correct program behavior.
Composition over Inheritance
A design principle favoring object composition (has-a relationships) over class inheritance (is-a relationships) for code reuse.
Dependency Injection
A design pattern where objects receive their dependencies from external sources rather than creating them internally.
SOLID Principles
Five design principles for writing maintainable, flexible object-oriented code: Single Responsibility, Open-Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion.
Observer Pattern
A design pattern where an object (subject) maintains a list of dependents (observers) that are notified automatically of state changes.
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