UML class diagrams basics in LLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a UML class diagram?

A UML class diagram is a visual representation that shows the structure of a system by displaying its classes, their attributes, methods, and the relationships between them.

beginner

What are the three main parts of a UML class diagram box?

The three main parts are: 1) Class name at the top, 2) Attributes (properties) in the middle, 3) Methods (operations) at the bottom.

beginner

What does an association relationship represent in a UML class diagram?

An association shows a connection between two classes, meaning objects of one class use or are linked to objects of another class.

intermediate

What is the difference between inheritance and composition in UML class diagrams?

Inheritance means one class is a specialized version of another (is-a relationship). Composition means one class contains another class as a part (has-a relationship) and controls its lifecycle.

intermediate

How is multiplicity shown in UML class diagrams and what does it mean?

Multiplicity is shown near the ends of association lines as numbers or ranges (e.g., 1, 0..*, *). It indicates how many instances of a class can be linked to instances of another class.

Which part of a UML class diagram shows the class's functions?

A The top compartment

B The bottom compartment

C The middle compartment

D Outside the box

The bottom compartment lists the methods or operations of the class.

What does a solid line with a hollow triangle arrow represent in UML?

A Inheritance

B Association

C Composition

D Dependency

A solid line with a hollow triangle arrow shows inheritance (generalization).

If a class 'Car' has a composition relationship with 'Engine', what does it mean?

A Car uses Engine temporarily

B Car is a type of Engine

C Car contains Engine and controls its lifecycle

D Car and Engine are unrelated

Composition means Car has an Engine as a part and controls its lifecycle.

What does multiplicity '0..*' mean in a UML association?

A Exactly zero instances

B One instance only

C At least one instance

D Zero or many instances

'0..*' means zero or many instances can be linked.

Which UML diagram focuses on showing classes and their relationships?

A Class diagram

B Use case diagram

C Sequence diagram

D Activity diagram

Class diagrams show classes and their relationships.

Describe the main components of a UML class diagram and their purpose.

Think about the box parts and how classes connect.

Explain the difference between inheritance and composition with simple examples.

Use real-life objects like animals or cars.