Polymorphism Using Methods

Polymorphism Using Methods

1. Two Kinds (beginner map!)

Compile-time (overloading: same name, different params — compiler picks!) vs Runtime (overriding: child remakes parent method — JVM picks by OBJECT!). Runtime = true polymorphism!

class Calc {
    int add(int a, int b) { return a + b; }
    double add(double a, double b) { return a + b; } // same name, different params!
    int add(int a, int b, int c) { return a + b + c; }
}
calc.add(1, 2);   // int version (compiler picks by args!)
calc.add(1.5, 2.5); // double version!

4. Rules (exam traps!)

• Overriding needs SAME signature + IS-A + non-static + non-private + covariant return ok.
• @Override annotation catches typos (soud() → error!).
• Overloading ≠ overriding (table: binding time, signature, class!).

5. Exam Points

• Overload vs override table + program — 7-10 marks, #1 polymorphism Q.
• Runtime trace (a.sound() → ?) — 5 marks, very frequent.