What does encapsulation in Java mean?

Encapsulation refers to binding data and methods together to form a class. It can hide the internal implementation details of a class and only expose some public interfaces for external access, thus improving the security and maintainability of the code.

In Java, encapsulation is achieved by using access modifiers (such as private, public, protected). By setting data members as private, direct access and modification of data is prevented, and can only be done through class methods. Additionally, class methods can also process, validate, and control data to ensure its validity and correctness.

The advantages of encapsulation include:

1. Enhancing data security by concealing the internal implementation details of a class to prevent direct access and modification of data.
2. Increase code maintainability: By encapsulating, it becomes easier to modify the internal implementation of a class without affecting external code.
3. Provide a simple interface: Encapsulate can provide a set of simple interfaces to make it easier for external code to use the functionality of the class.
4. Reduced coupling: Encapsulation can separate the internal implementation details of a class from external code, reducing dependencies between code and increasing flexibility and scalability.