Free Basic Design Pattern Question and Answers

Question 1

Give a subsystem's collection of interfaces a unified interface. It defines a higher level interface that facilitates use of the subsystem.

Accepted Answer

Facade

Answer

The Facade pattern provides a unified, higher-level interface to a set of interfaces in a subsystem. It defines a simpler interface that makes the subsystem easier to use, reducing complexity and promoting loose coupling between the client and the subsystem. This hides the intricate details of the subsystem's components.

Question 2

Define an operation that contains the basic structure of an algorithm while leaving some phases to subclasses. It enables subclasses to modify specific algorithmic stages without altering the algorithm's structure.

Accepted Answer

Template method

Answer

The Template Method pattern defines the basic structure of an algorithm in an operation, deferring some specific steps to subclasses. This allows subclasses to modify or implement certain stages of the algorithm without altering its fundamental structure. It ensures that the overall flow of the algorithm remains consistent while providing customization points.

Question 3

Enables sequential access to the components of an aggregate object without disclosing its underlying representation.

Accepted Answer

Iterator

Answer

The Iterator pattern provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation. It decouples the traversal logic from the aggregate object itself, allowing different traversal algorithms to be used and simplifying the aggregate's interface. This ensures controlled and consistent access to collections.

Question 4

Which statement regarding the Singleton design pattern is true.

Accepted Answer

All of the above

Answer

All the statements accurately describe the Singleton design pattern. It is a creational pattern that ensures a class has only one instance and provides a global point of access to it, typically through a static method, without requiring explicit object initialization by the client.

Question 5

Dynamically assign extra responsibilities to an object. It offers a versatile substitute for subclassing when it comes to extending functionality.

Accepted Answer

Decorator

Answer

The Decorator pattern dynamically attaches additional responsibilities to an object. It provides a flexible alternative to subclassing for extending functionality, allowing new behaviors to be added or removed at runtime. This 'wraps' the original object with new capabilities without altering its core class.

Pattern Design Practice Test

Pattern Design Practice Test

Free Basic Design Pattern Question and Answers