Podcast
Questions and Answers
What is the primary role of the Composite class in the context of the Composite Design Pattern?
What is the primary role of the Composite class in the context of the Composite Design Pattern?
What type of files can the Directory class contain?
What type of files can the Directory class contain?
What is the purpose of the Component class in the design pattern described?
What is the purpose of the Component class in the design pattern described?
What type of relationship exists between the Decorator and the ConcreteComponent?
What type of relationship exists between the Decorator and the ConcreteComponent?
Signup and view all the answers
Which method is responsible for adding files to the Directory class?
Which method is responsible for adding files to the Directory class?
Signup and view all the answers
What issue arises from overusing inheritance in the beverage class design?
What issue arises from overusing inheritance in the beverage class design?
Signup and view all the answers
What does the getSize() method in the Directory class compute?
What does the getSize() method in the Directory class compute?
Signup and view all the answers
In the provided implementation, what type does the TextFile class return in its getType() method?
In the provided implementation, what type does the TextFile class return in its getType() method?
Signup and view all the answers
How do ConcreteDecorators enhance the behavior of the component?
How do ConcreteDecorators enhance the behavior of the component?
Signup and view all the answers
What method do all subclasses of Beverage override?
What method do all subclasses of Beverage override?
Signup and view all the answers
In the context of the Composite Design Pattern, what does the term 'leaf' refer to?
In the context of the Composite Design Pattern, what does the term 'leaf' refer to?
Signup and view all the answers
Which of the following condiments is NOT listed in the coffee shop example?
Which of the following condiments is NOT listed in the coffee shop example?
Signup and view all the answers
What is the purpose of the File interface in this design pattern implementation?
What is the purpose of the File interface in this design pattern implementation?
Signup and view all the answers
How is the size calculated for the Directory object containing child files?
How is the size calculated for the Directory object containing child files?
Signup and view all the answers
In the approach to avoid class explosion, which variable type is added to the Beverage class?
In the approach to avoid class explosion, which variable type is added to the Beverage class?
Signup and view all the answers
Why is the cost() method not declared as abstract in the modified Beverage class design?
Why is the cost() method not declared as abstract in the modified Beverage class design?
Signup and view all the answers
What is the primary purpose of the Composite design pattern?
What is the primary purpose of the Composite design pattern?
Signup and view all the answers
Which of the following is NOT a characteristic of the Composite pattern?
Which of the following is NOT a characteristic of the Composite pattern?
Signup and view all the answers
In the context of the Composite pattern, what is a Leaf object?
In the context of the Composite pattern, what is a Leaf object?
Signup and view all the answers
What role does the Composite object play in the Composite pattern?
What role does the Composite object play in the Composite pattern?
Signup and view all the answers
Which of the following scenarios is most appropriate for applying the Composite pattern?
Which of the following scenarios is most appropriate for applying the Composite pattern?
Signup and view all the answers
How are Leaf and Composite objects related in the Composite pattern?
How are Leaf and Composite objects related in the Composite pattern?
Signup and view all the answers
When implementing a Composite design pattern, what is a key step to ensure uniform treatment of components?
When implementing a Composite design pattern, what is a key step to ensure uniform treatment of components?
Signup and view all the answers
Which of the following best illustrates the concept of the Composite pattern in real life?
Which of the following best illustrates the concept of the Composite pattern in real life?
Signup and view all the answers
What does the cost method in the abstract class Beverage signify?
What does the cost method in the abstract class Beverage signify?
Signup and view all the answers
What is the role of the Decorator pattern in the context of beverage selection?
What is the role of the Decorator pattern in the context of beverage selection?
Signup and view all the answers
Which class serves as the base class for both concrete components and decorators?
Which class serves as the base class for both concrete components and decorators?
Signup and view all the answers
In the given example, which of the following can be considered a concrete component?
In the given example, which of the following can be considered a concrete component?
Signup and view all the answers
What is the typical function of the abstract class CondimentDecorator?
What is the typical function of the abstract class CondimentDecorator?
Signup and view all the answers
How do Concrete Decorators differ from Concrete Components?
How do Concrete Decorators differ from Concrete Components?
Signup and view all the answers
What can be inferred about the description variable in the Beverage class?
What can be inferred about the description variable in the Beverage class?
Signup and view all the answers
What would be the immediate consequence of not overriding the cost method in a concrete component?
What would be the immediate consequence of not overriding the cost method in a concrete component?
Signup and view all the answers
What is the primary purpose of the getDescription method in the Beverage class?
What is the primary purpose of the getDescription method in the Beverage class?
Signup and view all the answers
Which statement accurately describes the relationship between DarkRoast and Beverage?
Which statement accurately describes the relationship between DarkRoast and Beverage?
Signup and view all the answers
What does the Mocha class do when it is constructed with a Beverage?
What does the Mocha class do when it is constructed with a Beverage?
Signup and view all the answers
How does the cost for a beverage decorated with Mocha calculate its total cost?
How does the cost for a beverage decorated with Mocha calculate its total cost?
Signup and view all the answers
What would b2 = new Mocha(b2) imply in terms of object-oriented principles?
What would b2 = new Mocha(b2) imply in terms of object-oriented principles?
Signup and view all the answers
Which class explicitly requires that the methods getDescription and cost be overridden?
Which class explicitly requires that the methods getDescription and cost be overridden?
Signup and view all the answers
What is the output of the following code snippet: Beverage b2 = new DarkRoast(); b2 = new Mocha(b2);?
What is the output of the following code snippet: Beverage b2 = new DarkRoast(); b2 = new Mocha(b2);?
Signup and view all the answers
Why must the cost method be overridden in the concrete classes of decorators?
Why must the cost method be overridden in the concrete classes of decorators?
Signup and view all the answers
What is the final cost of a beverage that is made up of DarkRoast, Mocha, and Whip?
What is the final cost of a beverage that is made up of DarkRoast, Mocha, and Whip?
Signup and view all the answers
Why can the Mocha class not be instantiated directly without a beverage?
Why can the Mocha class not be instantiated directly without a beverage?
Signup and view all the answers
What does the decorator pattern allow you to do with an object's behavior?
What does the decorator pattern allow you to do with an object's behavior?
Signup and view all the answers
What is a disadvantage of using the decorator pattern?
What is a disadvantage of using the decorator pattern?
Signup and view all the answers
When the cost method is called on the beverage that is a combination of DarkRoast and Mocha, what cost is initially returned from DarkRoast?
When the cost method is called on the beverage that is a combination of DarkRoast and Mocha, what cost is initially returned from DarkRoast?
Signup and view all the answers
In the example given, what is the role of the Whip class in relation to the other beverages?
In the example given, what is the role of the Whip class in relation to the other beverages?
Signup and view all the answers
How would the classes DarkRoast, Mocha, and Whip relate to each other in terms of class hierarchies?
How would the classes DarkRoast, Mocha, and Whip relate to each other in terms of class hierarchies?
Signup and view all the answers
What is necessary before you can instantiate the Mocha class?
What is necessary before you can instantiate the Mocha class?
Signup and view all the answers
Study Notes
STRUCTURAL DESIGN PATTERNS
- Structural design patterns compose classes or objects into larger structures, and then define ways to use these structures
COMPOSITE PATTERN
- Also known as: Object Tree
- Composite is a structural design pattern that lets you compose objects into tree structures and then work with these structures as if they were individual objects
- From the name, "Composite" means the combination or made from different parts
- This pattern provides a solution to operate on groups of objects and single objects in a similar way
- Real-life examples include file-directory structures, where a node can be a directory or a file
- Even though directories and files are different types of objects, they can be treated similarly (e.g., checking the size of a directory, which is the sum of sizes of all files within that directory)
- Another real-life example is employee hierarchy structure (CEO, managers, employees)
- All employees, managers and the CEO are instances of a person
- Structure of the composite pattern:
-
- Composite Object: An object that contains other objects. This can be a directory (file folder)
-
- Leaf Object: A single object that does not have children (e.g., a file).
-
WHERE CAN WE USE COMPOSITE PATTERN?
- When you want to represent a part-whole relationship in a tree structure (Objects can be represented in a tree structure hierarchy)
- Composite and individual objects are treated uniformly
- Need to define parent-child relationships
STEPS TO IMPLEMENT COMPOSITE DESIGN PATTERN
- Define leaf and composite objects as the same data type
- Implement an interface or extend a class
- Write common methods for all leaf and composite objects
- Leaf node performs its own desired behavior
- Composite object writes a customized function or each child of this node can call this function
STRUCTURE & PARTICIPANTS
- Component: Declares an interface for objects in the composition, and implements default behaviors common to all.
- Leaf: Represents leaf objects in the composition; doesn't have children; defines behavior for primitive objects.
- Composite: Defines behaviors for components having children; stores child components; implements child-related operations in the component interface
- Client: Manipulates objects in the composition through the component interface.
UML DIAGRAM FOR COMPOSITE DESIGN PATTERN IMPLEMENTATION
- Shown in the image will create an interface for " File ".
- Will have two different classes one for directory type and second for classes other than directory (.txt, .doc, etc).
IMPLEMENTING COMPOSITE DESIGN PATTERN IN JAVA
- Example for file directory structure
- Create child file and root directories.
- Get size of files and directories
COMPOSITE DESIGN PATTERN CLASS IMPLEMENTATION(JAVA)
- Classes for file and directory types (e.g.,
TextFile,Directory) -
DirectoryimplementsFileand stores a list ofFileobjects -
TextFileimplementsFileand has size
APPLICATION CLASS (JAVA)
- Implements
mainmethod for testing the code - Create
TextFileobjectschild1andchild2 - Create
Directoryobjectroot - Add
child1andchild2toroot - Print sizes of
child1androot.
PROS AND CONS OF COMPOSITE PATTERN
-
Pros:
- Data represented as a tree structure
- Same operations on different object types
- Reduces overhead for handling different types of objects
- Open/Closed Principle: introducing new elements without breaking existing code
-
Cons:
- Objects must be compatible
- Complexity can increase
DECORATOR PATTERN
- Decorator is a structural design pattern that lets you attach new behaviors to objects by placing them inside special wrapper objects that contain the behaviors
- Uses composition instead of inheritance to extend an object's functionality at runtime.
- Also known as Wrapper
- Wrap a component with any number of decorators (e.g., wrapping a gift, putting it in a box, wrapping the box).
- Change component behavior by adding new functionality before and/or after method calls to the component
- Provides an alternative to subclassing for expanding behavior
WHERE CAN DECORATOR PATTERN BE USED?
- Attach additional responsibilities to objects at runtime without altering code using these objects
- Use when it's hard to extend object behavior with inheritance
- Programming languages with the
finalkeyword used to prevent further extension of a class
UML CLASS DIAGRAM & PARTICIPANTS
- Component: Defines an interface for objects that can have responsibilities added dynamically
- Decorator: Decorators implement the same interface as the component; have a relationship with the object they extend (a has-a relationship).
- ConcreteComponent: Object to be enhanced dynamically. Inherits from Component.
- ConcreteDecorator: Decorators that enhance the state of the component, can add new methods, adding new behavior before or after existing methods.
COFFEE SHOP EXAMPLE
- Introduces a coffee shop, serving four beverage types (house blend, dark roast, decaf, espresso).
- Starts by using inheritance but quickly realizes this leads to many classes for various combinations of beverages and condiments.
- Example of "class explosion" caused by overuse of inheritance.
- Suggests alternative approach to handle condiments.
APPROACH 1
- Add boolean variables in
Beverageclass to represent condiments (milk, soy, mocha, whip) - Override the cost method in specific concrete
Beverageclasses
APPROACH 2
- Use Decorator pattern to dynamically add condiments
- Components are
Beverageclasses (DarkRoast, etc.) - Decorators are classes that add behavior to the
Beverageobject (e.g.,Whip,Mocha)
UML DIAGRAM OF DECORATOR PATTERN (EXAMPLE: MOCA AND WHIP DECORATIONS)
- Graphic shows a
DarkRoastclass. - Shows how
MochaandWhipcomponents add new behaviors, building up functionality
DECORATOR PATTERN CLASS DEFINITION (EXAMPLE: MOCA CLASS)
- Implments
Beverageclass - Has a beverage that it wraps
IMPORTANT NOTE ON DECORATOR PATTERN
- Decorator is a subclass of the Component class
- You cannot create a
ConcreteDecoratorwithout aConcreteComponent
PROS AND CONS OF DECORATOR PATTERN
-
Pros:
- Easily extend objects' behavior without creating subclasses.
- Add and remove behaviors at runtime
- Combine multiple behaviors using decorators.
-
Cons:
- Hard to remove a specific decorator from the stack.
- Code maintainability can be challenging as decorators can get numerous and similar; difficult to maintain and distinguish
QUESTIONS
- Composite: Composing Objects into Tree Structures
- Decorator: Adding Behaviors to Objects by Placing them Inside Wrappers
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the Composite pattern, a key structural design pattern that allows the composition of objects into tree structures. This quiz will cover its principles, real-life applications like file systems and employee hierarchies, and how it enables uniform treatment of individual and composite objects.
