OOPS

Inheritance

• Abstraction: extensibility.
• Interfaces: implementation.

public interface Operation {
  double add();
  double subtract();
  double multiply();
  double divide();
}

Polymorphism

• Overloading
• Overriding

Compile-Time

The call is resolved by the compiler. It is achieved by function overloading and operator overloading.

public class Example {
  public static int add(int a, int b) {
    return a + b;
  }
  public static double add(double a, double b) {
    return a + b;
  }
 
 public static void main(String args[]) {
    System.out.println(add(2, 3));
    System.out.println(add(2.0, 3.0));
  }
}

Run-Time

Creating the subclass object with the help of superclass object.

abstract class Vehicle {}

class Car extends Vehicle {}

class Truck extends Vehicle {}

...

Vehicle car = new Car();
Vehicle truck = new Truck();

Diamond Problem ?