How is the implementation of Java layering achieved?

In Java, layering is a common software architecture pattern that divides applications into multiple logical layers, each with different responsibilities and functions. Here is a common approach to implementing layering in Java.

1. Presentation Layer: This layer manages the logic and interactions of the user interface. It typically includes the user interface, controller, and components that interact directly with the user. The code in this layer is usually presented in the form of a graphical user interface (GUI) or web page.
2. Business Layer: This layer contains the core business logic and processing of an application. It is separate from the user interface and data storage, responsible for handling specific business requirements. This layer typically includes business logic, services, models, and related utility classes.
3. Data Access Layer: This layer is responsible for interacting with data storage, including databases, file systems, or other data sources. It provides persistent and access functions for data, allowing the business logic layer to read and write data from data sources. Typically, this layer includes data access objects (DAO), data models, and database connections.

The above is a common layered pattern, but can actually be adjusted and expanded according to specific needs and project size. The purpose of layering is to separate the different responsibilities and functions of an application to enhance the maintainability, scalability, and reusability of the code. Various design patterns and frameworks can be used to implement layered architecture, such as the MVC (Model-View-Controller) pattern, Spring framework, etc.