Doubt: K&B Self Test (Resolved and in errata)

[Gowher Naik]

hi
on page no 74(K&B book) there is question as follows.

Which declare compilable abstract class?
 
A.
public abstract class Canine{
public Bark speak();
}
 
B.
public abstract class Canine{
public Bark speak(){ }
}
 
C.
public class Canine{
public abstract Bark speak();
} 
 
D. 
public class Canine abstract{
public abstract Bark speak();
}  

A C and D is wrong.The book says B is correct but according to me the B is also wrong because there is no return type from speak method so this will not compile.

plz help
[ July 28, 2006: Message edited by: Barry Gaunt ]

[Shiaber Shaam]

It has return type of type "Bark" ... So it is not wrong .....

[Gowher Naik]

what i want to say is that method doesnot return anything

public abstract class Canine{
          public Bark speak(){
             //return statement is missing
          }
}

[Ramamoorthy Periasamy]

Well, The point here to understand is an abstract class can have non-abstract methods. NO need to check the code syntax unless its been asked explicitly

[Barry Gaunt]

I think that this should be corrected because the question is asking for a compilable abstract class. If there is nothing returned in the body of the method it will not compile. So either return a Bark object or change return type to void. Hopefully Bert has already spotted this one before.

[Barry Gaunt]

Yes, it is in the K&B 5.0 errata (see link at top of SCJP forum).

[d jones]

Could anyone please explain why Option A is not a compilable abstract class?


Thanks,
Dan

[Barry Gaunt]

Originally posted by d jones:
Could anyone please explain why Option A is not a compilable abstract class?


Thanks,
Dan

Change the return type to void and the compiler will scream the reason at you.