Combined 2 Bank (Sonali & Janata) Officer IT: Exam: 04.10.2024 (BIBM)প্রশ্ন ও সমাধান

Encapsulation bundles an object's data and the methods that operate on it into one unit, exposing only a controlled public interface and hiding internal representation.

Advantages:

• Data hiding/security - internal state cannot be corrupted by uncontrolled external access; only validated methods (getters/setters) can change it.
• Easier maintenance - the internal implementation (data storage, algorithm) can be changed freely as long as the public interface stays the same, without breaking other code.
• Reduced complexity for users - callers only need to know the public methods, not internal details, lowering cognitive load.
• Easier debugging/testing - because access is funneled through a small set of methods, it is easy to trace which method mutated a value.

Inheritance lets a new (derived/child) class acquire the attributes and behaviors of an existing (base/parent) class.

Advantages:

• Code reuse - common fields/methods are written once in the base class and reused by every subclass, reducing duplication and development time.
• Hierarchical modeling - naturally represents "is-a" relationships (e.g. Manager is-a Employee), mirroring real-world taxonomies.
• Extensibility/polymorphism - subclasses can override or extend base behavior, enabling polymorphic code that works uniformly across a family of related types.
• Easier maintenance - a fix or improvement in the base class automatically propagates to all subclasses.

classDiagram
    class Employee {
      -string name
      -double salary
      +getSalary() double
    }
    class Manager {
      -List~Employee~ team
      +getSalary() double
    }
    Employee <|-- Manager

Exam takeaway: encapsulation protects and simplifies how data is used; inheritance promotes reuse and hierarchical extensibility - together they are the pillars that let OOP systems scale and stay maintainable as they grow.