Inheritance and interface notation in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to show that class Dog inherits from class Animal.

LLD

class Dog [1] Animal:

Drag options to blanks, or click blank then click option'

A:

B(Animal)

C( )

D[Animal]

Attempts:

3 left

💡 Hint

Common Mistakes

Using a colon instead of parentheses

Using square brackets instead of parentheses

Leaving the parentheses empty

In most object-oriented languages, inheritance is shown by placing the parent class name in parentheses after the child class name.

2fill in blank

medium

Complete the code to declare that class Car implements the interface Vehicle.

LLD

class Car [1] Vehicle:

Drag options to blanks, or click blank then click option'

Aimplements

B(Vehicle)

C: Vehicle

D<Vehicle>

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of the keyword

Using colon instead of 'implements'

Using angle brackets

In many languages, the keyword implements is used to show that a class follows an interface.

3fill in blank

hard

Fix the error in the code to correctly show that class Bird inherits from Animal and implements Flyer.

LLD

class Bird [1] Animal, Flyer:

Drag options to blanks, or click blank then click option'

Aimplements

B<Animal, Flyer>

C(Animal, Flyer)

D: Animal, Flyer

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'implements' keyword with multiple parents

Using colon with multiple parents

Using angle brackets

When a class inherits from multiple classes or interfaces, they are listed inside parentheses separated by commas.

4fill in blank

hard

Fill both blanks to correctly show that class SmartPhone inherits from Phone and implements Camera.

LLD

class SmartPhone [1] Phone [2] Camera:

Drag options to blanks, or click blank then click option'

A(

Bimplements

C)

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'implements' keyword incorrectly

Using colon instead of parentheses

Not closing the parentheses

In some languages, inheritance and interface implementation are shown by listing parent classes and interfaces inside parentheses.

5fill in blank

hard

Fill both blanks to correctly declare class Tablet inherits from Device, implements TouchScreen, and is abstract.

LLD

abstract class Tablet {BLANK_1}} Device {{BLANK_2}} TouchScreen{

Drag options to blanks, or click blank then click option'

Aextends

Bimplements

C;

D{

Attempts:

3 left

💡 Hint

Common Mistakes

Using ';' instead of '{' to start class body

Mixing up 'extends' and 'implements'

Omitting the opening brace

In many languages, extends shows inheritance, implements shows interface implementation, and class body starts with '{'.

Practice

1. What does the notation <|-- represent in system design diagrams?

easy

A. Dependency, where one class depends on another

B. Interface implementation, where a class follows a set of rules

C. Inheritance, where one class is a specialized version of another

D. Aggregation, where one class contains another

Solution

1. Step 1: Understand notation meanings

   The notation <|-- is used to show inheritance in system design diagrams.

2. Step 2: Differentiate from interface notation

   Interface implementation uses <|.., not <|--.

3. Final Answer:

   Inheritance, where one class is a specialized version of another -> Option C

4. Quick Check:

   Inheritance = <|-- [OK]

Hint: Inheritance uses solid arrow <|-- [OK]

Common Mistakes:

• Confusing inheritance with interface implementation
• Mixing aggregation with inheritance notation
• Assuming dependency uses <|--

2. Which of the following is the correct notation for a class implementing an interface?

easy

A. Class <|-- Interface

B. Class <|.. Interface

C. Interface <|-- Class

D. Interface <|.. Class

Solution

1. Step 1: Recall interface implementation notation

   Interface implementation is shown by a dashed arrow <|.. from class to interface.

2. Step 2: Verify direction and notation

   The arrow points from the class to the interface, so Class <|.. Interface is correct.

3. Final Answer:

   Class <|.. Interface -> Option B

4. Quick Check:

   Interface implementation = <|.. from class to interface [OK]

Hint: Interface uses dashed arrow <|.. from class [OK]

Common Mistakes:

• Reversing arrow direction between class and interface
• Using solid arrow for interface implementation
• Confusing interface and inheritance notation

3. Given the following UML snippet:

interface IAnimal
class Dog <|.. IAnimal
class Labrador <|-- Dog

Which statement is true?

medium

A. IAnimal inherits from Dog and Labrador

B. Labrador implements IAnimal and inherits from Dog

C. Dog inherits from Labrador and implements IAnimal

D. Dog implements IAnimal and Labrador inherits from Dog

Solution

1. Step 1: Analyze interface implementation

   Dog implements IAnimal, shown by <|.. from Dog to IAnimal.

2. Step 2: Analyze inheritance

   Labrador inherits from Dog, shown by <|-- from Labrador to Dog.

3. Final Answer:

   Dog implements IAnimal and Labrador inherits from Dog -> Option D

4. Quick Check:

   Interface = <|.., Inheritance = <|-- [OK]

Hint: Dashed arrow = interface, solid arrow = inheritance [OK]

Common Mistakes:

• Mixing inheritance and interface directions
• Assuming interface inherits classes
• Confusing which class inherits which

4. Identify the error in this UML notation:

class Vehicle <|.. Car
interface Drivable <|-- Vehicle

medium

A. Vehicle cannot implement Car because Car is a class

B. Drivable cannot inherit Vehicle because interfaces use dashed arrows for inheritance

C. Arrow directions are reversed for both lines

D. No error, notation is correct

Solution

1. Step 1: Check first line meaning

   Vehicle <|.. Car means Vehicle implements Car, but Car is a class, not an interface, so this is invalid.

2. Step 2: Check second line meaning

   Drivable <|-- Vehicle means Drivable inherits Vehicle, but Drivable is an interface and Vehicle a class, so invalid.

3. Final Answer:

   Vehicle cannot implement Car because Car is a class -> Option A

4. Quick Check:

   Classes implement interfaces only [OK]

Hint: Classes implement interfaces, not other classes [OK]

Common Mistakes:

• Allowing classes to implement classes
• Reversing inheritance arrow direction
• Ignoring interface vs class roles

5. You are designing a system where Smartphone inherits from Device and implements two interfaces: Camera and GPS. Which UML notation correctly represents this?

hard

A. Smartphone <|-- Device
Smartphone <|.. Camera
Smartphone <|.. GPS

B. Device <|-- Smartphone
Smartphone <|.. Camera
Smartphone <|.. GPS

C. Device <|.. Smartphone
Camera <|-- Smartphone
GPS <|-- Smartphone

D. Smartphone <|.. Device
Camera <|.. Smartphone
GPS <|.. Smartphone

Solution

1. Step 1: Identify inheritance direction

   Smartphone inherits from Device, so arrow <|-- points from Smartphone to Device: Smartphone <|-- Device.

2. Step 2: Identify interface implementation

   Smartphone implements Camera and GPS interfaces, so dashed arrows <|.. point from Smartphone to each interface.

3. Step 3: Verify all notations

   Smartphone <|-- Device
   Smartphone <|.. Camera
   Smartphone <|.. GPS

   correctly shows inheritance and interface implementation directions.

4. Final Answer:

   Smartphone <|-- Device Smartphone <|.. Camera Smartphone <|.. GPS -> Option A

5. Quick Check:

   Inheritance arrow points to parent, interface arrow dashed from class [OK]

Hint: Inheritance arrow points to parent class, interface arrow dashed from class [OK]

Common Mistakes:

• Reversing inheritance arrow direction
• Using solid arrow for interface implementation
• Pointing interface arrows from interface to class