Java Classes and Objects: From Definition to Instantiation, the Basics of Object-Oriented Programming

The core of Object-Oriented Programming (OOP) is to abstract real-world entities into "classes" (object templates containing attributes and methods), and then simulate operations through "objects". A class like `Person` includes attributes such as `name` and `age`, and a method like `sayHello`. Objects are created using the `new` keyword (e.g., `Person person = new Person()`), and members are accessed using the `.` operator (for assignment or method calls). Constructor methods can initialize attributes (e.g., `Person(String name, int age)`). It is important to follow naming conventions (class names start with a capital letter, members with lowercase), default values, object independence, and encapsulation (member variables are recommended to be `private` and accessed via `getter/setter` methods). Mastering classes and objects is fundamental for subsequent learning of encapsulation, inheritance, and polymorphism.