Singleton - Ensure that only one instance of a class is created and Provide a global access point to the object.

Singleton pattern should be used when we must ensure that only one instance of a class is created and when the instance must be available through all the code. A special care should be taken in multithreading environments when multible threads must access the same resources throught the same singleton object.

Factory(Simplified version of Factory Method) - Creates objects without exposing the instantiation logic to the client and Refers to the newly created object through a common interface.

Factory pattern should be used when: - a framework delegate the creation of objects derived from a common superclass to the factory - we need flexibility in adding new types of objects that must be created by the class.

Factory Method - Defines an interface for creating objects, but let subclasses to decide which class to instantiate and Refers to the newly created object through a common interface.

Factory Method pattern should be used when:
- a framework delegate the creation of objects derived from a common superclass to the factory
- the base factory class does not know what concrete classes will be required to create - delegates to its subclasses the creation of concrete objects
- factory subclasses subclasses are aware of the concrete classes that must be instantiated

Factory method pattern, compared to Factory pattern replace the factory with an abstract class and a set of concrete factories subclasses. The subclasses are responsible for creating concrete product objects; for factory method is possible adding new product classes without changing the abstract factory. The same result can be achieved for simplified factory pattern if reflection is used.

Abstract Factory - Offers the interface for creating a family of related objects, without explicitly specifying their classes.

Abstract Factory should be used when:

* A system should be configured with one of multiple families of products
* A system should be independent of how its products are created, composed and represented
* Products from the same family should be used all together, products from different families ahould not be used togheter and this constraint must be ensured.
* Only the product interfaces are revealed, the implementations remains hidden to the clients.

Builder - Defines an instance for creating an object but letting subclasses decide which class to instantiate and Allows a finer control over the construction process.

Prototype - Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype.