How is polymorphism implemented in java

What is polymorphism

The three major characteristics of object-oriented: encapsulation, inheritance, and polymorphism. From a certain perspective, encapsulation and inheritance are almost always prepared for polymorphism.

The definition of polymorphism

refers to allowing objects of different types to respond to the same message. That is, the same message can behave in many different ways depending on the person to whom it is sent. (Sending a message is a function call)

Technology to implement polymorphism

Dynamic binding (dynamic binding) refers to judgment during execution The actual type of the referenced object, and its corresponding method is called according to its actual type.

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The role of polymorphism

Eliminate the coupling relationship between types.

Three necessary conditions for the existence of polymorphism

1. There must be inheritance;

2. There must be overwriting;

3. The parent class reference points to the subclass object.

The benefits of polymorphism:

1. Substitutability.

Polymorphism is replaceable for existing code. For example, polymorphism works for the Circle class, but it also works for any other circular geometry, such as a torus.

2. Extensibility.

Polymorphism enables scalability of code. Adding new subclasses does not affect the polymorphism, inheritance, and operation and operation of other features of existing classes. In fact, it is easier to add new subclasses to obtain polymorphic functions. For example, after implementing the polymorphisms of cones, semicones, and hemispheres, it is easy to add polymorphisms of the sphere class.

3. Interface-ability.

Polymorphism is achieved by the superclass providing a common interface to subclasses through method signatures, which are then completed or overridden by subclasses.

4. Flexibility.

It embodies flexible and diverse operations in the application and improves usage efficiency.

5. Simplicity.

Polymorphism simplifies the code writing and modification process of application software. This feature is particularly prominent and important when dealing with calculations and operations on a large number of objects.

The implementation method of polymorphism in Java: interface implementation, inheriting the parent class for method rewriting, and method overloading in the same class.

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