Why Does OOP Allow Class-Level Access to Private Fields Instead of Object-Level Access?

Encapsulation and Object-Level Access in OOP

Object-oriented programming (OOP) is designed around the concept of encapsulation, which restricts access to an object's private fields to the class that defines them. However, in the given code snippet, it's possible to access the account private field of another Person object. This behavior raises the question:

Why does OOP allow class-level access to private fields rather than object-level access?

The answer lies in the design principles of OOP and the advantages of limiting access to specific objects.

According to Artemix, who provided an insightful response on another forum, the private modifier enforces the encapsulation principle. It ensures that external entities cannot modify an object's internal state, as internal processes may change over time. If external code could access private fields, any changes to those processes would require modifying all external code, making maintenance and evolution difficult.

By restricting access to class-level, instances of the same class are always aware of the implementation details of their private methods and fields. This simplifies code maintenance and ensures consistency across all instances.

In other words, object-level access would allow external code to manipulate an object's state in unexpected ways, potentially leading to inconsistencies and bugs. Class-level access, on the other hand, allows the object itself to control access to its private fields, ensuring that only authorized methods can modify its internal state.

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