What is the main purpose of encapsulation in object-oriented programming?

Encapsulation is a fundamental principle of object-oriented programming that focuses on restricting direct access to certain components of an object. This concept ensures that an object's internal state cannot be altered directly from outside the object. Instead, access to this state is controlled through public methods (often called getters and setters) that either allow or restrict the modification of attributes.

The primary purpose of encapsulation is to protect the integrity of the object's data and to promote a clear separation between the object's internal implementation and the external interactions with that object. By doing so, encapsulation enhances code maintainability, supports data hiding, and helps in managing complexity by bundling data and the methods that operate on that data into a single unit or class.

In contrast, the other options do not accurately reflect the core purpose of encapsulation. Creating a complex user interface pertains more to graphical programming and design rather than encapsulation. Allowing multiple classes to inherit from a single class refers to inheritance, another object-oriented principle, rather than encapsulation. Increasing performance, while important in programming, is not the primary focus of encapsulation; instead, encapsulation may introduce some overhead due to additional method calls for accessing data.