Java Examples - Tested

Interfaces.java

// An interface can extend any number of interfaces but a class can extend only one class (multiple inheritance is not 
// supported in Java - diamond problem)

// Diamond Problem
// When A and B class have the same method and when the class C extends A, B 
// implementing the method name from either of A or B, compiler doesn't from which
// class the method should be overridden or considerd.

interface Vehicle {
    void accelerate();
}

// Extend Vehicle interface so that consumers of Vehicle interface doesn't have to implement
// methods specific to IndianVehicle
// Or add default or static methods to existing interface so that consuments don't have to implement them.

// Default methods enable you to add new functionality to existing interfaces and ensure binary 
// compatibility with code written for older versions of those interfaces
interface IndianVehicle extends Vehicle {
    String manufacurer(String manufacturer);
    
    default String country() {
        return "India";
    }
}

class Bike implements Vehicle {
    public void accelerate() {
        System.out.println("General Bike acc");
    }
}

class IndianBike implements IndianVehicle {
    public void accelerate() {
        System.out.println("Indian bike acc");
    }
    
    public String manufacurer(String manf) {
        return manf;
    }
    
   // Extending interfaces that contain default methods:
   // 1. Not mention the default method at all, which lets your extended interface inherit the default method.
   // 2. Redeclare the default method, which makes it abstract.
   // 3. Redefine the default method, which overrides it. 
}

class Main {
    public static void main(String[] args) {
        Vehicle bike = new Bike();
        bike.accelerate();
        
        IndianVehicle indianBike = new IndianBike();
        indianBike.accelerate();
        System.out.println("Bike country: " + indianBike.country());
        System.out.println("Bike manf: " + indianBike.manufacurer("Bajaj"));
        
    }
}