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For example, a parent class, A, can have two subclasses B and C. Both B and C's parent class is A, but B and C are two separate subclasses. Hybrid inheritance Hybrid inheritance is when a mix of two or more of the above types of inheritance occurs. An example of this is when a class A has a subclass B which has two subclasses, C and D.
Composition over inheritance (or composite reuse principle) in object-oriented programming (OOP) is the principle that classes should favor polymorphic behavior and code reuse by their composition (by containing instances of other classes that implement the desired functionality) over inheritance from a base or parent class. [2]
The name open–closed principle has been used in two ways. Both ways use generalizations (for instance, inheritance or delegate functions) to resolve the apparent dilemma, but the goals, techniques, and results are different. The open–closed principle is one of the five SOLID principles of object-oriented design.
The doctrine of composition over inheritance advocates implementing has-a relationships using composition instead of inheritance. For example, instead of inheriting from class Person, class Employee could give each Employee object an internal Person object, which it then has the opportunity to hide from external code even if class Person has ...
In class-based programming, inheritance is done by defining new classes as extensions of existing classes: the existing class is the parent class and the new class is the child class. If a child class has only one parent class, this is known as single inheritance , while if a child class can have more than one parent class, this is known as ...
In general, the further down in the hierarchy a class appears, the more specialized its behavior. When a message is sent to an object, it is passed up the inheritance tree starting from the class of the receiving object until a definition is found for the method. This process is called upcasting.
Not all languages support multiple inheritance. For example, Java allows a class to implement multiple interfaces, but only inherit from one class. [22] If multiple inheritance is allowed, the hierarchy is a directed acyclic graph (or DAG for short), otherwise it is a tree. The hierarchy has classes as nodes and inheritance relationships as links.
In object-oriented programming, behavior is sometimes shared between classes which are not related to each other. For example, many unrelated classes may have methods to serialize objects to JSON. Historically, there have been several approaches to solve this without duplicating the code in every class needing the behavior.