Object-Oriented Programming (OOP) in Java is a programming paradigm that organizes software design around objects, which encapsulate both data and behaviors. In Java, an object is an instance of a class, which serves as a blueprint for creating objects. This approach allows developers to model real-world entities, making it easier to manage complex systems by breaking them down into smaller, manageable components.

Key concepts of OOP in Java include:

1. Classes and Objects: Classes define the structure and behavior of objects. An object is created from a class and can have its own unique attributes and methods.

2. Inheritance: This allows a new class to inherit properties and methods from an existing class, promoting code reusability.

3. Encapsulation: This principle involves wrapping data (attributes) and methods (functions) into a single unit, which helps in protecting the data from unauthorized access.

4. Polymorphism: This allows objects of different classes to be treated as objects of a common superclass, enabling flexibility in code.

Understanding these principles is essential for writing scalable and maintainable applications in Java ¹⁴⁵.