Inheritance and interface notation in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Interface Implementation

In a low-level design diagram, which notation best represents a class implementing an interface?

A A dashed line with a closed arrowhead pointing from the class to the interface

B A solid line with a closed arrowhead pointing from the class to the interface

C A solid line with an open arrowhead pointing from the interface to the class

D A dashed line with an open arrowhead pointing from the class to the interface

💡 Hint

Think about how interfaces are usually shown differently from inheritance in UML.

In UML, a class implementing an interface is shown with a dashed line and an open arrowhead pointing to the interface.

❓ Architecture

intermediate

Inheritance Relationship in Class Diagrams

Which notation correctly shows inheritance between two classes in a low-level design diagram?

A A solid line with an open arrowhead pointing from the child class to the parent class

B A dashed line with a closed arrowhead pointing from the parent class to the child class

C A solid line with a closed arrowhead pointing from the parent class to the child class

D A dashed line with an open arrowhead pointing from the child class to the parent class

💡 Hint

Inheritance arrows usually point from the child to the parent class.

Inheritance is shown with a solid line and an open arrowhead pointing from the subclass to the superclass.

❓ scaling

advanced

Handling Multiple Interfaces in Design

When a class implements multiple interfaces, how should this be represented in a low-level design diagram?

A Draw multiple solid lines with closed arrowheads from the class to each interface

B Draw a single solid line with an open arrowhead from the class to a combined interface

C Draw multiple dashed lines with open arrowheads from the class to each interface

D Draw a dashed line with an open arrowhead from each interface to the class

💡 Hint

Think about how each interface is separately implemented.

Each interface implemented by a class is shown with its own dashed line and open arrowhead pointing to the interface.

❓ tradeoff

advanced

Choosing Between Inheritance and Interface

Which statement best explains a key tradeoff when choosing inheritance over interface implementation in system design?

A Inheritance reduces coupling and increases flexibility compared to interfaces

B Inheritance allows code reuse but limits flexibility due to tight coupling

C Interfaces prevent any form of polymorphism in the system

D Interfaces provide code reuse but increase coupling between classes

💡 Hint

Think about how inheritance shares code but can create dependencies.

Inheritance shares code but creates tight coupling, while interfaces increase flexibility without code reuse.

❓ estimation

expert

Estimating Diagram Complexity with Interfaces and Inheritance

Given a system with 10 classes where each class implements 3 interfaces and inherits from 1 parent class, how many total relationship lines (inheritance + interface) will appear in the low-level design diagram?

A 40 lines

B 50 lines

C 20 lines

D 30 lines

💡 Hint

Calculate inheritance lines plus interface implementation lines for all classes.

Each class has 1 inheritance line and 3 interface lines, so total lines = 10 * (1 + 3) = 40.