Question from Marcus Green mock exam

[janne s]

Which of the following represent valid code if it is the entire contents of a file called whitney.java?


1 abstract final class whitney{}
2 public final class whitney extends Object{}
3 public abstract class whitney{}
4 protected class whitney{}

The Correct Answer

2) public final class whitney extends Object{}
3) public abstract class whitney{}


I think answer 2 is wrong. If i'm worng pls explain.

Thank you in advance
jaya
[ November 08, 2004: Message edited by: jaya merugu ]

[Toms Liepins]

Hi jaya, i believe that you have not understood the 'final' modifier. Final class/method can not be extended/overriden, however it DOES NOT mean that the final class ITSELF could not extend another nonfinal class. Answer 2 is correct (if you don't believe, try compiling

[Krishna Srinivasan]

Answer 2,3 are correct.
why answer 2 is wrong. canu you tell the reason?
answer 2 syntax is perfectly valid.

[Atul Chandran]

Every class extends Object class implicitly. But explicitly mentioning it does not result in an error. An analogy to instance variables will make it clear.

String a;//a will be assigned null by default.
String b=null;//is legal and null is assigned to b.
similarly
class A{} //A will extend Object by default
class B extends Object {} //legal and B extends Object class.

[Marcus Green]

It may seem a somewhat obscure point to test if you know that everything inherits from Object, even if it is not explicitly stated. However the great ancestor Object class provides some functionality that is used in threading, so it does have a practical application.