Читать книгу OCP Oracle Certified Professional Java SE 17 Developer Study Guide - Jeanne Boyarsky - Страница 63

In Java programs, classes are the basic building blocks. When defining a class, you describe all the parts and characteristics of one of those building blocks. In later chapters, you see other building blocks such as interfaces, records, and enums.

To use most classes, you have to create objects. An object is a runtime instance of a class in memory. An object is often referred to as an instance since it represents a single representation of the class. All the various objects of all the different classes represent the state of your program. A reference is a variable that points to an object.

In the following sections, we look at fields, methods, and comments. We also explore the relationship between classes and files.