Questions
5 of 12
1What is Inheritance? What is the 'IS-A' relationship?
2What are the different types of Inheritance? (Single, Multilevel, Hierarchical)
3Why does Java/C# not support Multiple Inheritance of classes? (The Diamond Problem)
4How do you solve the Diamond Problem? (Interfaces/Mixins)
5What is the difference between 'IS-A' (Inheritance) and 'HAS-A' (Composition)?
6Why is Composition often preferred over Inheritance? (Fragile Base Class problem)
7Can a subclass access the private members of its parent class?
8What is the purpose of the base or super keyword?
9Can you prevent a class from being inherited? How? (Sealed/Final)
10What happens if a Base class constructor throws an exception? Does the Derived object get created?
11Can you change the access modifier of a base class method in a derived class? (Hiding vs Overriding)
12What is the difference between 'Overriding' and 'Hiding/Method Shadowing'?
OOPSOOPS
Basics
Inheritance and Composition
Polymorphism
Interfaces and Abstract Classes
Access Modifiers and Scope
Advanced Concepts and Design Principles
Trees
Real-World Design and Architecture Scenarios
05 / 12

What is the difference between 'IS-A' (Inheritance) and 'HAS-A' (Composition)?

Difficulty: 2/10

IS-A vs HAS-A

IS-A represents specialization and is normally modeled through inheritance. HAS-A represents ownership, collaboration or composition, where one object contains or uses another object. For example, a Car IS-A Vehicle, while a Car HAS-A Engine. In architecture, HAS-A relationships are generally more flexible because components can be replaced independently and the owning class does not need to inherit the implementation details of its dependency.

javascript
  1. 1

    IS-A: Represents specialization or substitutability.

  2. 2

    HAS-A: Represents composition, ownership or collaboration.

  3. 3

    Inheritance creates a stronger coupling between types.

  4. 4

    Composition allows dependencies to be replaced or configured.

  5. 5

    A good design distinguishes domain specialization from implementation reuse.

Follow-up Questions

  • Why is composition more flexible?
  • Can an object have multiple HAS-A relationships?
  • How does dependency injection relate to composition?
  • Give a real-world example where inheritance is inappropriate.
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