Creational design patterns govern how objects are instantiated; the Singleton pattern restricts a class to exactly one instance by combining a private constructor with a static/class-level access method that controls instance creation, and is generally considered an anti-pattern because it breaks object-oriented design principles (subclassing can bypass the single-instance guarantee), removes control over whether an accessed instance is new or existing, hinders testability, and is prone to race conditions in multi-threaded contexts. The Object Pool pattern is a generalization of the Singleton that manages a fixed-size collection of reusable instances rather than exactly one, tracked via separate "free" and "in-use" collections with acquire/release operations, and is useful when object creation is expensive and instances are needed only temporarily. Both patterns belong to the creational category of object-oriented design patterns, one of three general pattern categories (creational, structural, behavioral) that respectively address object creation, object/class composition, and algorithm or communication variation.
Creational design patterns govern how objects are instantiated; the Singleton pattern restricts a class to exactly one instance by combining a private constructor with a static/class-level access met…