Encapsulation: encapsulation is one of the basic principles of object-oriented programming. It forms an entity called a class by combining data and related operations (methods). Class encapsulates data and operations and provides interfaces for accessing and manipulating data. Encapsulation can not only protect the security of data, but also hide the internal implementation details and improve the maintainability and reusability of code.
Inheritance: Inheritance is an important concept in object-oriented programming, which allows you to create new classes and inherit properties and methods from existing classes. Through inheritance, subclasses can inherit the properties and methods of the parent class, and can be extended or modified on this basis. Inheritance contributes to the reuse and extension of code, establishes the hierarchical relationship between classes, and improves the structure and readability of code.
Polymorphism: Polymorphism is another key concept in object-oriented programming, which allows different objects to respond differently to the same message. Polymorphism can be achieved through inheritance and interfaces. In polymorphism, an object can exist in many forms, and different behaviors can be selected according to specific conditions. This flexibility improves the scalability and maintainability of the code, and also provides higher code abstraction and flexibility.