What does encapsulation in object-oriented programming primarily protect?

Encapsulation in object-oriented programming primarily protects data integrity by restricting direct access to an object’s internal state and requiring all interactions to be performed through well-defined interfaces. This concept ensures that the object's data cannot be modified inadvertently or inappropriately from outside the object, which helps maintain consistent and valid states within objects throughout their lifecycle. By providing methods to access or modify the data, encapsulation ensures that relationships and constraints are honored, thereby preserving the integrity of the data.

In contexts where other concepts like system security, code quality, or interface design are mentioned, they often leverage encapsulation but don't directly define its primary purpose. The focus on protecting data integrity is what sets encapsulation apart as a cornerstone of effective object-oriented design, ensuring that only valid operations can be performed on an object’s data, thus leading to more robust and maintainable code.