Notes on Private Classes in Object-Oriented Programming

Overview

• Discussion on classes: public vs. private classes.
• Example of an employee class containing a date object.
• Public classes can be accessed by other classes.

Private Classes

Definition

• A private class is not accessible outside its enclosing class.
• Often used for encapsulation of data and implementation details.

Example: Linked List

• A linked list consists of nodes that typically have:
  • A value (data)
  • A pointer to the next node
• Node class can be defined as a private class within the linked list class.

Justification for Using Private Classes

• Encapsulation: Hides the implementation details (node structure) from users of the linked list.
• Users interact with linked list values without needing to know about nodes' pointers:
  • Simplifies user interaction and reduces complexity.

Implementation Details

• In a private node class within a linked list:
  • Node can have private fields for data and next pointer.
  • Private class can access other private instance variables of the linked list, such as size.

Inner Classes

• A private class defined inside another class is often called an inner class.
• Inner classes have access to the enclosing class's private members.
  • This is beneficial for operations that need to interact with the enclosing class's state.

Key Points

• Encapsulation: To improve data hiding, private classes can be used to prevent exposure of implementation details.
• Access Control: Combining private classes with interfaces allows controlled access to an object’s state.
  • Public methods usually provide this access but may need constraints.
• Utility of Private Classes: Although their use may seem minimal, they play a crucial role in maintaining clean, manageable code architecture.