When should you use Singleton and when Prototype?

Singleton is used when a single instance of a class is needed throughout the application, for example, for managing configuration, logging, or connection pools. It guarantees that the object's state is unified and accessible globally.

Prototype is applied when there is a need to create multiple copies of objects with the same structure but different states. This is convenient if creating an object is costly, and you can clone an already configured instance.

Example:

• Singleton: the Logger class, where all parts of the application write to the same log.
• Prototype: a document template that is cloned and filled with different data.

The choice depends on the task: if a single shared object is needed — Singleton; if many similar objects are required — Prototype.