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Which singleton variant would you use in each case?

Your application doesn't use multithreading.

Your application uses multithreading and you don't want to create the singleton object unless/until it is necessary.

Your application uses multithreading, but the singleton object is always created or its creation doesn't pose an overhead.

Clients must be aware of strategies

Which of these are consequences of the strategy pattern?

Hierarchy of strategy classes

Alternative to sub-classing

The total number of classes decreases

Repeated code

Depend on abstraction, not concrete implementations

Match the principles with their key idea

It’s better to use many client-specific interfaces than one big general-purpose interface

A class should have only one reason to change.

Classes should be open for extension but closed for modification

Select the design principles that are applied in the Observer Pattern

The strategy principle

The multi-tasking principle

Strive for loosely coupled designs

Interface segregation principle

Hollywood Principle: don't call us we call you

Select the differences between the Factory Method Pattern and the Abstract

Factory Pattern.

The factory method is a method and the abstract factory is an object.

Factory Method encapsulates instantiation and Abstract Factory does not.

Abstract Factory is not considered officially a pattern.

The abstract factory allows to encapsulate the instantiation of families of related classes.

The Factory Method uses inheritance while the Abstract Factory uses delegation.

Select all that are true about decorators:

A decorator maintains a reference to the component object it wraps.

Objects can be decorated at runtime (with as many decorators as desired).

Decorators have the same supertype as the object they decorate.

A decorator adds its own behaviour before and/or after delegating to the object it decorates.

A decorator must be a subclass of the concrete component it wraps.

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Write the pattern's name