What is a singleton pattern?

The singleton pattern is a design pattern that restricts a class to a single instance, ensuring that only one object of that class can be created throughout the application. This is particularly useful when you need to control access to resources, such as database connections or configuration settings, where having multiple instances could lead to inconsistent states or performance issues. The singleton pattern typically involves creating a private constructor and a static method that allows for controlled access to the instance, often with lazy initialization to ensure that the instance is only created when it's first needed. This design pattern is essential when it's crucial to have a single point of control and access within an application, thereby simplifying resource management and ensuring consistency across different parts of the application.