Polymorphism in Java OOP

Polymorphism is a core concept in object-oriented programming (OOP) that allows objects of different classes to be treated as objects of a common superclass. It’s one of the four major OOP principles, alongside encapsulation, inheritance, and abstraction. Polymorphism in Java enables a single interface to be used for a general class of actions. The specific action is determined by the exact nature of the situation. There are two types of polymorphism in Java: compile-time (static) and runtime (dynamic) polymorphism.

Compile-Time Polymorphism

Compile-time polymorphism, also known as static polymorphism, is achieved through method overloading. Method overloading allows a class to have multiple methods with the same name but different parameters.

Example of Compile-Time Polymorphism:

Runtime Polymorphism

Runtime polymorphism, or dynamic polymorphism, is achieved through method overriding. In method overriding, a subclass provides a specific implementation of a method already present in its superclass.

Example of Runtime Polymorphism:

Key Points about Polymorphism

  • Flexibility and Scalability: Polymorphism offers flexibility and scalability to the code. It allows the extension of code without modifying the existing code.
  • Use in APIs: It’s widely used in implementing interfaces and inheritance, making it fundamental for designing flexible and scalable APIs in Java.
  • Enhances Code Reusability: Polymorphism enhances code reusability through the ability to use the same interface for different underlying forms of data types.


Polymorphism is a pivotal concept in Java and OOP, enabling objects of different classes to interact with each other through a common interface. By understanding and effectively using polymorphism, developers can write more flexible, scalable, and maintainable code. Whether through compile-time or runtime polymorphism, this OOP principle helps achieve a high level of abstraction and code reusability.

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