The singleton pattern is one of the best-known design patterns. This pattern ensures that only one instance of a class exists throughout the application running inside the virtual machine.

A singleton is a class whose instance can be created only once. This exists until the application is up and running. A singleton class provides a single access point that has to be used to get the instance of the class. It restricts the number of instances of a class to one and controls the creation of instances of the class.

 A singleton class in an application is used when managing things such as memory, connection pools, threads, logging, and the registry. This ensures the consistency, reliability, and correctness of the data that classes handle in the application.