overriding related problem

[pranav jog]

Hi,

is it necessary that sub class must have same return type at the time of method overriding?

[Nicola Garofalo]

From K&B Book

The return type must be the same as, or a subtype of, the return type declared
in the original overridden method in the superclass.

[Raza Mohd]

hi Pranav,

yeah it is necessary that the return type of the overriding method should be same.
however, the access modifier can be different.

keep in mind:: We can not make the access modifier more restricted in the subclass.
eq. A overridden method cant be declared as private, if it is public in Super class.

restriction level for access modifier::::

public < protected < default<private

[Vijitha Kumara]

Raza Mohd wrote:yeah it is necessary that the return type of the overriding method should be same.

Not necessarily, read the above quote from the K&B.
And Welcome to JavaRanch, Pranav

[Raza Mohd]

yes! i missread vijitha..
type may be a subtype of the overridden method in superclass.

like Arraylist is a subtype of List.

[Rob Spoor]

Keep in mind that this feature (called covariant returns) is added in Java 5.0. In Java 1.4 and before Raza's statement is correct - the return types must be the same.

[Raza Mohd]

thanks for the confirmation Rob!

[Campbell Ritchie]

Welcome to the Ranch

You really ought to be looking, not at the K&B book, but at the Java™ Language Specification, which is the official documentation. That confirms that K&B are in fact correct, but there is a subtle difference: you can understand K&B

I am not sure what

R1 = | R2 |

means.

[David Newton]

Absolute value :D

(More likely it means this, which I guess is sort of like that.)

[Campbell Ritchie]

Thank you, David. You are right: absolute value is obviously correct. Or is it "obvious value is absolutely correct"?

[David Newton]

Absolutely :)

(Some day I'm going to re-read the JLS now that I'm actually starting to know Java...)