Singleton

The Singleton design pattern receives this name because it can only have a single instance of a specific class for the entire application; this is achieved by preventing the creation of multiple instances of the same class, as it typically happens with the new operator, and imposing a private constructor and a static method to get that instance.

The objective of this pattern is to guarantee the creation of a single instance of a specific class and the existence of a global reference for the entire application.

These are the components included in this pattern:

• Client: It's the component requesting an instance of the Singleton class.
• Singleton: It's the class implementing the Singleton pattern, from which only one instance can exist during the entire life-cycle of the application.

1. The client requests for an instance of the Singleton through the getInstancemethod.
2. The Singleton checks if the instance has already been created, if not, a new instance will be created.
3. Either the newly created instance or the already existing instance is returned.

Real-world example

By implementing the Singleton design pattern, we are going to create an application for managing the system settings from a sole central point. Therefore, when the application starts, the initial settings will be loaded up and stay available.

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