Difference Between Composition and Inheritance (With Table)

Through the use of previous versions to create new software using the concepts of reusability is referred to as reusable code in programming. In computer technology companies, code reusability is regarded as a critical productivity function. In entity programming, there have been two basic ways to define these relationships: inheritance and composition.

Composition vs Inheritance

The difference between composition and inheritance is that composition is used to build a class having a “has-a” relationship rather than an “is-a” relationship as in inheritance. Inheritance allows member functions through one class to become the property of another without having to code them directly in the class. 

Class inheritance is reinstated with article composition. Composition is described as the use of one entity within another. Since it’s simple to construct complicated classes utilizing previously published, well-designed classes as components, one can always use an object as a field within another class. All of that is referred to as composition.

In OOP, inheritance refers to the process by which one entity acquires the characteristics of another. It’s among the most effective ways to enforce code reuse in OOP. A new class may be formed by creating parent-child relations with current classes by using inheritance. Classes can inherit frequently used states and behavior from some of the other classes owing to object-oriented computing.

Comparison Table Between Composition and Inheritance

Parameters of ComparisonCompositionInheritance
SignificanceWe just declare a type that we want to utilize in composition, and it can store several implementations that can vary at runtime.We define the class that we are adopting (superclass) in inheritance, and it cannot be altered at execution.
Class CombiningThe ability to combine functionality from distinct classes is provided through composition.We can only extend one class in this case; in other words, many classes cannot be extended because Java does not enable multiple inheritances.
FunctionalityComposition allows us to test the functionality of the classes we’re using without having to worry about whether they’re parent or child classes.Inheritance necessitates the use of a parent class in order to test a child class.
Code ReutilizationEven code from final classes can be reused thanks to composition.The final class cannot be extended through inheritance.
Relationship It is a “has-a” situation.It’s an “is-a” situation.

What is Composition?

A composition is a form of aggregation in which ownership is implied. There is a dependence because one object is dependent on another. Consider the following objects: a school object and a classroom object. The school object is required for the classroom object to exist. The classroom object is damaged if the school object is destroyed. As a result, these two items are interdependent. As such, it is indeed a composition. To put it another way, we call something a composition if it can’t exist without the whole.

A further connection between classes given by OOP is composition, also known as a has-a relation. If somehow the characteristics of one object must be incorporated into the features of another, the relationship necessitates composition. To create a new class from the parent class, each class’s object must be declared as a member of the current class.

Composition is described as the use of an object inside another object. An entity could be used as a field in any class regularly. In composition, they use an entity that is part of a class. Item composition, unlike class inheritance, is described continuously at run-time by entities obtaining connections to other objects.

What is Inheritance?

Inheritance is when a new class uses the attributes and methods of an existing class. This pre-existing class is referred to as the parent class, superclass, or foundation class. The new class is referred to as a child, sub, or derived class. Due to inheritance, the creator does not even have to write the code from the start. He may use inheritance to reuse the attributes and methods of a derived idea in the new class. As a result, inheritance improves code reuse. Inheritance can be single-level, multi-level, hierarchical, Multi, and Hybrid in nature.

If we want to build a fresh class but there seems to be one with some of the code we need, we may extract our new class from the current one. We could reuse the current class’s properties and methods instead of writing them ourselves. A subclass inherits most of its superclass’s representatives. Constructors aren’t participants, so they aren’t passed down to subclasses, but the superclass’s function Object() { [native code] } can be called from the subclass. 

Main Differences Between Composition and Inheritance

  1. We just declare a type that we want to utilize in composition, and it can store several implementations that can vary at runtime. On the other hand, We define the class that we are adopting (superclass) in inheritance, and it cannot be altered at execution.
  2. The ability to combine functionality from distinct classes is provided through composition, whereas We can only extend one class in this case; in other words, many classes cannot be extended because Java does not enable multiple inheritances.
  3. Composition allows us to test the functionality of the classes we’re using without having to worry about whether they’re parent or child classes. Inheritance necessitates the use of a parent class in order to test a child’s class.
  4. Even code from final classes can be reused thanks to composition, whereas the final class cannot be extended through inheritance.
  5. Composition is a “has-a” situation, whereas Inheritance is an “is-a” situation.

Conclusion

Since complicated classes are simpler to construct using previously written, well-designed classes, you’ll sometimes want to use an object as a field within another class. That’s where the ability of composition comes in. Since inheritance allows you to reuse code by expanding a class with little effort, it’s a useful tool for creating relationships between classes.

Composition is preferable in general because it allows you to use an object without losing its internal data, which is where composition comes in handy. While inheritance has its drawbacks, object composition poses similar performance issues in terms of object formation and destruction.

References

  1. https://dl.acm.org/doi/abs/10.1145/2161996.2162002
  2. https://www.sciencedirect.com/science/article/pii/S0890540112000399
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