Dutch Bangla Bank Ltd.; Probationary Officer (Software) Written Test: 2016প্রশ্ন ও সমাধান

Method overloading and method overriding are the two forms of polymorphism found in OOP languages such as Java and C++.

• Overloading (compile-time polymorphism): several methods in the same class share a name but differ in their parameter list (count, type, or order). The compiler selects the right version based on the arguments used at the call site.
• Overriding (run-time polymorphism): a subclass re-implements a method that already exists in its superclass, keeping the same name, parameters, and return type. The version actually executed is decided at run time from the real object type (dynamic dispatch).

Aspect	Overloading	Overriding
Classes involved	Same class	Parent and child class
Method signature	Must differ	Must be identical
Binding time	Static (compile-time)	Dynamic (run-time)
Purpose	Flexible behaviour for varying input	Specialise inherited behaviour
Return type	May differ	Must be same/covariant

class Calculator {                    // Overloading
    int add(int a, int b) { return a + b; }
    double add(double a, double b) { return a + b; }
}

class Animal {                        // Overriding
    void sound() { System.out.println("Some sound"); }
}
class Dog extends Animal {
    @Override
    void sound() { System.out.println("Bark"); }
}

Exam takeaway: Overloading = same class, different signature, resolved at compile time; overriding = parent-child, same signature, resolved at run time through the vtable/dynamic dispatch mechanism.