OOP focuses on key ideas like abstraction, encapsulation, inheritance, and polymorphism. These principles help create clean, scalable, and efficient applications.
Composition and inheritance are two key techniques for structuring code. They show how different objects relate. This helps developers keep code simple and reuse it better. Choosing between composition and inheritance is important. The wrong choice can create tightly coupled systems. This can make future changes expensive and hard to manage.
Traditionally, inheritance helped define relationships between classes. It allowed child classes to take on behaviours from parent classes. This approach worked well for simple hierarchies. However, it often caused problems. These included deep inheritance chains, less flexibility, and high coupling. As a result, large-scale systems became harder to maintain.
Composition has become popular. It offers a more scalable, modular, and maintainable solution to these challenges. Composition lets you create objects by using references to other objects. This approach promotes loose coupling and improves code reusability.
Why is this important?
In today's world of microservices, cloud computing, and software-as-a-service (SaaS), deciding between composition and inheritance can have a big effect.
- Code maintainability – how easy it is to update, refactor, and extend code.
- Performance – How efficiently objects interact, especially in large-scale systems.
- Scalability – Whether the architecture supports rapid feature additions and modifications.
- Pricing models – How software complexity impacts cloud computing and infrastructure costs.
In this blog, we will explore composition and inheritance. We’ll examine their main differences, how they operate, the performance trade-offs, and how they influence pricing in software services. By the end, you'll know when to use inheritance and when to choose composition. You'll also see how both methods affect system design and scalability.
What is inheritance?
Inheritance is a feature in OOP. It allows a child class to inherit properties and methods from a parent class. This forms a hierarchy. The child class inherits attributes and methods from the parent. This cuts down on code duplication.
It follows the "is-a" relationship. If Class B inherits from Class A, it is a type of Class A. For example, a Dog class can inherit from an Animal class since a dog is an animal.
How inheritance works
- A child class can use all public and protected methods and attributes from its parent class.
- It allows developers to reuse existing functionality without rewriting it.
- Child classes can override parent class methods to modify behaviour.
- Enables polymorphism, where a parent reference can be used to refer to a child object.
Characteristics of Inheritance
- Code Reusability
- Inheritance reduces redundancy. It allows child classes to use the methods and attributes from the parent class.
- This eliminates code duplication and streamlines maintenance.
- Hierarchical Structure
- It promotes an organised class hierarchy, grouping related functionalities under a common structure.
- This structure is beneficial when defining categories of objects that share common behaviours.
- Method Overriding
- The child class can change a method from the parent class to create a customized version.
- This lets subclasses create their own behaviour while keeping a shared interface.
- Supports Polymorphism
- With method overriding, different objects can execute the same method in different ways.
- This enables dynamic method dispatch, improving code flexibility and extensibility.
Limitations of Inheritance
While inheritance is a powerful concept, it comes with certain drawbacks:
- Tightly Coupled Code: Changes in the parent class affect all subclasses. This makes modifications difficult.
- Too many levels of inheritance can make debugging hard and slow down performance. This can cause problems, like using more memory.
- Rigid hierarchies: inheritance creates a strict structure. This makes it tough to adjust to new needs.
- Can Cause Fragile Base Class Issues: A tiny change in the superclass might need updates in all subclasses. This can make maintenance harder.
Developers often choose composition instead of inheritance in modern software design. This is due to the limits of inheritance. Let’s explore composition in detail
Example of Inheritance in Java
class Animal {
void makeSound() {
System.out.println("Some generic sound...");
}
}
class Dog extends Animal {
@Override
void makeSound() {
System.out.println("Barking...");
}
}
public class InheritanceExample {
public static void main(String[] args) {
Animal myDog = new Dog();
myDog.makeSound(); // Output: Barking...
}
}
In this example, the Dog class comes from the Animal class. It changes the makeSound() method to give it unique functionality.
What is composition?
Composition is a key design principle in Object-Oriented Programming (OOP). It explains how to build complex objects by using simpler, reusable parts. This method is better than relying on inheritance. Composition lets objects hold references to other objects. This means they can gain functionality flexibly instead of extending a class for behaviour. This shows the “has-a” relationship. Here, an object is made up of one or more independent parts.
This approach makes modularity, scalability, and maintainability better. That’s why it is a popular choice in today’s software world, like microservices, APIs, and cloud-native apps.
Why choose composition over inheritance?
Inheritance creates tight coupling. This makes it hard to change or add features without impacting all subclasses. Composition offers more flexibility. You can modify, replace, or reuse individual parts without changing the whole system.
Characteristics of Composition
- More flexible than inheritance.
- Unlike inheritance, which enforces a rigid class hierarchy, composition provides dynamic behaviour adjustments.
- You can build objects with several independent parts. Each part has its own specific function.
- This allows for better code reuse without the downsides of deep inheritance trees.
- Encapsulation & Loose Coupling
- Composition ensures that objects interact through well-defined interfaces, reducing dependencies between classes.
- Changes in one class don’t affect dependent classes, preventing unexpected side effects.
- This makes refactoring and modifying existing code much easier than with inheritance.
- No issues with deep inheritance.
- Deep inheritance trees make debugging and code maintenance difficult.
- Composition solves this issue by organising behaviour through object relationships, not class hierarchies.
- This is especially useful in large-scale applications where functionality evolves over time.
- Easier Maintenance & Testing
- Since each component is self-contained, it can be tested, modified, and debugged independently.
- Unit testing becomes easier. Each part of the system can be tested on its own, without needing the whole object hierarchy.
- Supports the Single Responsibility Principle (SRP), so each class has a clear role.
When to Use Composition?
Use Composition when:
- You need flexibility in how objects behave.
- You want modules that can be replaced or upgraded independently. This way, the whole system won’t be affected.
- You are building microservices, APIs, or cloud-native applications that require a modular architecture.
- Follow best practices like the SOLID principles. Pay special attention to the Dependency Inversion Principle (DIP).
Avoid inheritance when:
- The behaviour of objects is subject to frequent changes.
- You want to reduce dependency between classes.
- You are designing for scalability and maintainability in large applications.
Developers can use composition rather than inheritance. This makes software easier to change and grow. This approach helps keep the code efficient, scalable, and durable over time.
Example of Composition in Java
class Engine {
void start() {
System.out.println("Engine starting...");
}
}
class Car {
private Engine engine; // Car HAS-A Engine
Car() {
engine = new Engine();
}
void drive() {
engine.start();
System.out.println("Car is driving...");
}
}
public class CompositionExample {
public static void main(String[] args) {
Car myCar = new Car();
myCar.drive();
}
}
Here, the Car class is composed of an Engine instance instead of inheriting from it, making the design more modular and reusable.
Key Differences Between Composition and Inheritance
| Feature | Inheritance | Composition |
| Definition | Deriving a class from another class. | Using objects of other classes inside a class. |
| Relationship Type | "Is-a" relationship. | "Has-a" relationship. |
| Code Reusability | High but rigid. | High and flexible. |
| Encapsulation | Lower (due to tight coupling). | Higher (loose coupling). |
| Flexibility | Hard to modify without affecting child classes. | Easy to modify without breaking dependencies. |
| Performance | Can slow down execution due to deep inheritance chains. | Generally faster since objects communicate via references. |
| Testing & Debugging | Harder due to dependencies. | Easier due to independent, self-contained components. |
| Best for | Modeling real-world hierarchies (e.g., Animal -> Dog). | Modular applications, service-based architectures. |
Performance Considerations: Composition vs Inheritance
The choice between composition and inheritance significantly impacts performance in software systems. Inheritance has been a way to reuse code, but it can slow down complex applications. Composition boosts execution efficiency. This suits modern software architectures better. This includes cloud-based apps, microservices, and event-driven systems.
Inheritance can lead to performance bottlenecks.
Using deep inheritance trees can negatively impact performance in multiple ways:
- Increased Method Resolution Time
- In inheritance-based architectures, finding the right method can take longer. Java and other OOP languages need to look through the class hierarchy to locate the method to invoke.
- This leads to longer execution times, especially with many layers of inheritance.
- Virtual method calls add runtime overhead.
- In OOP, method calls usually happen at runtime. This is common, especially with polymorphism.
- This is especially problematic in large-scale applications with extensive use of polymorphism.
- Base class modifications require subclass recompilation.
- Any changes made to the base class affect all subclasses.
- This requires recompiling dependent components, increasing development and testing time.
- This problem gets worse in enterprise applications. Here, keeping backward compatibility is key.
Composition improves execution efficiency.
Composition enhances performance by skipping the added burden of deep inheritance trees. Objects interact through references, not class hierarchies. This makes execution more efficient.
- Objects interact via references.
- Instead of being part of a rigid hierarchy, objects reference other objects dynamically.
- This reduces processing time. Method lookups skip checking several parent classes.
- Loose coupling enables optimised garbage collection.
- Inheritance-based models tend to retain unnecessary dependencies, making garbage collection less efficient.
- Composition helps manage objects independently. This lets unused objects get garbage collected faster, improving memory performance.
- More efficient memory management
- Inheritance forces objects to carry inherited data, even if it is not required.
- Composition allows objects to hold only the essential references they need. This results in lower memory usage.
In modern cloud computing and distributed systems, performance optimization is critical. Using composition reduces execution time, optimises memory use, and improves scalability.
Impact on Software Services & Pricing
The inheritance vs. composition debate goes beyond performance. It also impacts scalability, maintenance costs, and pricing models in software development, SaaS, and cloud computing.
1. Development & Maintenance Costs
Inheritance-Based Development
- Higher maintenance costs are due to tightly coupled classes.
- Changes in the base class need updates in all subclasses. This can slow down development.
- Recommended for well-defined, stable hierarchies where structural changes are minimal.
Composition-Based Development
- Lower maintenance costs as components evolve independently.
- Changes to one module do not affect others, reducing debugging complexity.
- Ideal for APIs, microservices, and plug-and-play architectures, where modularity is crucial.
2. Scalability in Cloud Services
Choosing between inheritance and composition impacts how applications scale in the cloud.
Inheritance-Based Services
- Requires an entire service redeployment if the base class is modified.
- Less modular, which makes horizontal scaling difficult.
- Changes cascade through the hierarchy, making upgrades riskier.
Composition-Based Services
- Encourages modular microservices, where individual services can scale independently.
- Works well with containerisation technologies (Docker, Kubernetes), improving deployment efficiency.
- Microservices can be deployed without affecting the entire system, ensuring better uptime and availability.
For businesses using cloud platforms like AWS, Azure, and GCP, compositional design makes it easier to scale up.
3. Pricing Models in Cloud Computing
Software pricing in cloud environments is directly influenced by architectural choices.
Monolithic (Inheritance-Based) Pricing
- More expensive due to larger, interconnected dependencies.
- Deep inheritance hierarchies lead to higher resource usage, increasing operational costs.
- Higher compute and storage expenses, as services must scale together.
Microservices (Composition-Based) Pricing
- Cheaper since individual services scale independently.
- Lower compute costs as only the required components are run.
- It is effective with serverless models such as AWS Lambda, Azure Functions, and Google Cloud Functions. This means costs are based on usage, not fixed always-on instances.
Cloud-based startups and businesses can save money and boost performance by choosing composition over inheritance.
When to Use Composition Over Inheritance?
Use Composition when:
- You need flexibility in behavior (e.g., APIs, cloud-based applications).
- Code should be loosely coupled and easy to modify.
- You’re designing microservices, event-driven architectures, or scalable distributed systems.
- You need efficient, maintainable, and testable code with lower memory overhead.
Use Inheritance when:
- You’re modeling clear hierarchies (e.g., Animal -> Dog)
- You need to reuse large amounts of logic without composition overhead.
- Performance is not a major concern, and hierarchy-based code organization is preferable.
The choice between composition and inheritance is a key decision in software design. Inheritance allows code reuse, but it also creates tight coupling. This can lead to tough maintenance and slower performance. Composition offers flexibility, modularity, and scalability. This is the best option for modern setups, such as microservices and cloud computing.
Cloud developers, software architects, and DevOps teams can create better systems. Knowing these principles makes systems more efficient, scalable, and cost-effective.
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