Composition

Composition is the practice of creating other class objects in your class. In such a scenario, the class which creates the object of the other class is known as the owner and is responsible for the lifetime of that object.

Composition relationships are Part-of relationships where the part must constitute part of the whole object. We can achieve composition by adding smaller parts of other classes to make a complex unit.

So, what makes the composition so unique?

In composition, the lifetime of the owned object depends on the lifetime of the owner.

Example

A car is composed of an engine, tires, and doors. In this case, a Car owns these objects so a Car is an Owner class and tires,doors and engine classes are Owned classes.