What are the advantages of composition in…

Composition offers the following advantages:

Flexibility: Allows easy replacement or modification of parts of the object by changing or swapping the objects it contains, without altering the container class itself.
Reusability: Enables the creation of complex objects by combining simpler, reusable objects.
Loose coupling: Reduces dependencies between classes. Changing the internal representation of one component does not affect classes that use the container object, as long as the component interface remains unchanged.
Testability: Simplifies testing, as components can be tested individually.
Improved readability and maintainability: The code becomes more understandable because each part of the system has a clearly defined role.

Unlike inheritance, which creates an "is-a" relationship, composition creates a "has-a" relationship. This helps avoid problems with "fragile base class" issues and inheritance hierarchies that can become too complex and rigid.

Example:

Instead of creating multiple classes through inheritance:

// Not recommended
class Vehicle { /* ... */ }
class Car extends Vehicle { /* ... */ }
class Truck extends Vehicle { /* ... */ }

You can use composition to add functionality:

// Recommended
interface Engine { void start(); }
class GasEngine implements Engine { public void start() { /* ... */ } }
class ElectricEngine implements Engine { public void start() { /* ... */ } }

class Vehicle {
    private Engine engine;

    public Vehicle(Engine engine) {
        this.engine = engine;
    }

    public void start() {
        engine.start();
    }
}

This allows easy creation of different types of vehicles with different engines without the need to create a new inheritance tree for each combination of features.

What are the advantages of composition in object-oriented programming?