Explain the concept of composition in object-oriented programming.

Composition in object-oriented programming is a principle where one object contains another object as part of its structure to utilize its functionality.

Unlike inheritance, where a class extends the behavior of a base class, composition allows creating complex objects from simple ones by combining them.

Example:

class Engine {
    void start() {
        System.out.println("Engine started");
    }
}

class Car {
    private Engine engine = new Engine();

    void startCar() {
        engine.start();
        System.out.println("Car is running");
    }
}

Here, the Car class contains an Engine object and uses its methods, demonstrating composition.