What is the difference between composition and inheritance?

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Both composition and inheritance are fundamental concepts of object-oriented programing, which define relationships between classes and their objects. Composition is the process of constructing complex objects by combining simpler ones. Inheritance is the process of creating a new (derived) class that inherits attributes and behaviors of an existing (base) class. The main difference is in the way they establish relationships between objects and classes. Java Course in Pune

A class can contain an instance of another as a "member" with composition. The containing class is in a relationship of "has-a" with the contained class. A Car class, for example, may contain instances from the Engine, Wheel and Chassis classes. These components are usually created and managed in the Car class. Composition provides greater flexibility and modularity as objects contained within the class can be swapped out or modified easily without affecting the containing one.

Contrary to inheritance, the "is-a relationship" between classes is established by inheritance. Inheritance lets a class inherit methods and attributes from another class. This promotes code reuse and extends the functionality of the base. A Truck class can inherit from the Vehicle class and gain access to all of its methods and properties. It is easier to organize code and create a hierarchy among classes with inheritance. However, it can also lead to a tight class hierarchy and rigidity.

Both composition and inheritance promote code reuse and modular design. However, their approaches to establishing relationships among classes are different. Composition focuses on combining simple objects to create complex ones. This promotes flexibility and modularity. Contrastingly, inheritance is focused on creating new classes from existing ones. This encourages code reuse and hierarchical relations. Both concepts are useful tools for object-oriented programs, with their own strengths and uses.