Java

Question

what is upcasting and downcasting in Java ? plz explain through code.

Answer 1

Example classes:
class Animal { ... }
class Fox extends Animal { ... }
class Cat extends Animal { ... }

UPCASTING:

Fox fox = new Fox();
Animal animal = fox;

//We know Fox is Animal, so upcasting is "riskless", any Fox or Cat object can be placed into Animal variable, so can be upcasted.

DOWNCASTING:

Animal animal = new Fox();
Fox fox = (Fox) animal;

//Not all Animal is Fox, so it is "risky" to say, it is. If not, than ClassCastException is thrown:

Animal animal = new Cat();
Fox fox = (Fox) animal;
--> does throw ClassCastException

//That's why it is usually encapsuled into a check if:

if (animal instanceof Fox) {
Fox fox = (Fox) animal;
//or directly:
((Fox)animal).doFoxThing;
}

Answer 2

Thank you Magyar David