What is the advantage of Singleton design pattern?

Example of singleton classes is Runtime class, Action Servlet, Service Locator . Private constructors and factory methods are also an example of the singleton class.

Primarily due to the fact that a singleton holds an instantiated object, whereas static classes do not, singletons have the following advantages over static classes: Singletons can implement interfaces . Singletons can be passed as parameters. Singletons can have their instances swapped out (such as for testing purposes …

In software engineering, the singleton pattern is a software design pattern that restricts the instantiation of a class to one “single” instance . This is useful when exactly one object is needed to coordinate actions across the system.