Type Casting in Java

[yogesh doshi]

Why below code is valid it even do not throw any runtime exception??

class A {
public int getCode(){ return 2;}
}
class AA extends A {
public void doStuff() {
}
public static void main(String args[])
	{
	  A a=null;
	  A aa=null;
	  aa=(AA)a;
	}
}

[Henry Wong]

The null reference value may be cast to any reference type -- as all reference variables may have the value of null.

Henry

[Narayana Bojja]

As Henry already explained , I also want to give my opinion. Here you probably expected NullPointerException or ClassCastException. But that doesn't occur. NullPointerException occurs when you call a method/variable on reference variable which is  null. So here  you are not calling anything on references , so no chance of  NullPointerException. ClassCastException occurs when you type cast super class reference to sub class reference type if super class reference variable is pointing to super class object. Here super class reference variable is not  pointing to any object. So no chance of ClassCastException. Overall you don't get any exceptions here.