java.lang.ClassException: A cannot be cast into B

Question

I implemented this code:

class A {
    //some code
}
class B extends A {
    // some code
}

class C {
    public static void main(String []args)
    {
              


        

Answer 1

It's simple. Think that when you are extending you have to use is a

B `is a` A
A `is not` B

A more realistic example

class Animal{
}

class Dog extends Animal{
}

class Cat extends Animal{
}

A DOG IS A Animal AN ANIMAL IS NOT a DOG necessary (Example : a cat is not a dog, and a cat is an animal)

You are getting runtime exception cause , in runtime realize that that animal is not a dog, this is call downcasting and is not safe what are you trying to do.