What are the applicable scenarios for the singleton pattern?

Applicable scenarios for the singleton pattern include: 1. When a class can only have one instance and customers can access it from a well-known access point; 2. When this only instance should be extensible through subclassing , and customers should be able to use an extended instance without changing their code.

##Applicability

• When a class can only have one instance and the client When it can be accessed from a well-known access point

• When this unique instance should be extensible through subclassing, and customers should be able to use an extended instance without changing code

Singleton pattern

Ensures that a class has only one instance and provides a global access point to access it. Let the class itself be responsible for saving its unique instance and providing a method to access that instance. This is the singleton pattern.

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