General Design patterns & principles

"Identify the aspects of your application that vary and separate them from what stays the same." results in:

• More flexibility in your systems.

• Less classes in your systems.

• Less interfaces in your systems.

• Tighter coupling of your system.

"Program to an interface, not an implementation." means:

• Do not program to an abstract superclass.

• Program to a supertype.

• If possible, put everything in one class.

• Go for a concrete implementation whenever possible.

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"Favor composition over inheritance." says:

• Use the Composite Pattern instead of inheritance.

• IS-A is always better than HAS-A

• HAS-A can be better than IS-A

• Do not use inheritance.

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"Strive for loosely coupled designs between objects that interact." does NOT mean:

• When two objects are loosely coupled, they can interact, but have very little knowledge of each other.

• Interdependency between objects is minimized.

• Loosely coupled designs allow to build flexible OO systems.

• Interdependency between objects is maximized.

The Dependency Inversion Principle says:

• Depend upon abstraction. Do not depend upon concrete classes.

• Don't call us, we call you.

• Program to an interface, not an implementation.

• Favor composition over inheritance.

The Single Responsibility Principle says

• Favor composition over inheritance.

• A class should have only one reason to change.

• Depend upon abstractions.Do not depend upon concrete classes.

• Classes should be open for extensions, but closed for modification.

Which text below describes the Template Method pattern best?

• Subclasses decide how to implement steps in an algorithm.

• Allows (a group of) objects to be notified when some state changes.

• Encapsulates interchangeable behaviours and uses delegation to decide which one to use.

• Template method pattern changes the interface of one or more classes.

What is NOT a correct statement for the Hollywood Principle?

• Call us, we don't call you.

• A low-level component never calls a high-level component directly.

• It is a way to prevent dependency rot.

• High-level components control when and how low-level components participate in the computation.

Which text below describes the Strategy Pattern best?

• Encapsulates interchangeable behaviours and uses delegation to decide which one to use.

• Provides a way to traverse a collection of objects without exposing the collection's implementation.

• Client treats collections of objects and individual objects uniformly.

• Simplifies the interface of a group of classes.

What is a proper design principle?

• Program to an interface, not an implementation.

• Use abstract classes to implement what varies.

• The number of classes should be identical with the number of interfaces.

• Put what varies and what stays the same together. Do ti so that starting with an abstract class, all other classes inherit in a clever way.