Unable to understand reason for ClassCastException

[Priyadarshan Kelkar]

Please can someone explain why I get a class cast exception

package com.scjp.practice.oo;

class Animal{
	 void eat(){
		System.out.println("Animal eating food");
	}
}

class Horse extends Animal{

	void eat(){
		System.out.println("Horse eating grass ");
	}
	
	void bray(){
		System.out.println("Eeeee haw haw haw");
	}
}


public class TestInheritance {

	public static void main(String[] args) {
				
		Animal a = new Animal();
		Horse h = new Horse();
		
		Horse ha = (Horse) a;
		ha.eat();
	}	

}

Thanks in advance.

[Mehmet Gunacti]

Hi,

because at runtime "a" refers to an "Animal" object, which you can't cast to a Horse.

This one would work :

Animal a = new Animal();  
Horse h = new Horse();  
a = h;
          
Horse ha = (Horse) a;  
ha.eat();

[Seetharaman Venkatasamy]

ClassCastException

[Priyadarshan Kelkar]

Thanks Mehmet !

[Tommy Delson]

You need an "instanceof" test before the downcast to ensure, otherwise, it will throws an exception.

See my post and discussion on a similar topic for more info.
https://coderanch.com/t/544105/java-programmer-SCJP/certification/downcasting-or-upcasting-ref-variable

Reread K & B on "Reference Variable Casting (Objective 5.2)" Chapter 2 page 116 for more insight and test the new code to clear your doubt.

Hope it help...

[Hama Kamal]

Priyadarshan Kelkar wrote:Please can someone explain why I get a class cast exception

package com.scjp.practice.oo;

class Animal{
	 void eat(){
		System.out.println("Animal eating food");
	}
}

class Horse extends Animal{

	void eat(){
		System.out.println("Horse eating grass ");
	}
	
	void bray(){
		System.out.println("Eeeee haw haw haw");
	}
}


public class TestInheritance {

	public static void main(String[] args) {
				
		Animal a = new Animal();
		Horse h = new Horse();
		
		Horse ha = (Horse) a;
		ha.eat();
	}	

}

Thanks in advance.

because a is not an instance of Horse ...in order to downcast it should have been upcasted before ,, like

Animla a = new Horse();
Horse ha = (Horse)a;