Very nice discussion, Adrian!
Mark
-----Original Message-----
From: Adrian Janssen
Sent: Friday, July 11, 2003 4:01 AM
To answer question 1:
You can hide ancestor variables by declaring a variable in a descendant
class with the same name. However the ancestor class's variable is still
accessible via the super keyword. Hence this is generally NOT considered
overriding because if you call a method in the ancestor from the descendant
class, the ancestor method will use the old variable.
Here is an excerpt from the language specification that explains it more
completely:
8.3.3.1 Example: Hiding of Class Variables
The example:
class Point {
static int x = 2;
}
class Test extends Point {
static double x = 4.7;
public static void main(String[] args) {
new Test().printX();
}
void printX() {
System.out.println(x + " " + super.x);
}
}
produces the output:
4.7 2
because the declaration of x in class Test hides the definition of x in
class Point, so class Test does not inherit the field x from its superclass
Point. Within the declaration of class Test, the simple name x refers to the
field declared within class Test. Code in class Test may refer to the field
x of class Point as super.x (or, because x is static, as Point.x). If the
declaration of Test.x is deleted:
class Point {
static int x = 2;
}
class Test extends Point {
public static void main(String[] args) {
new Test().printX();
}
void printX() {
System.out.println(x + " " + super.x);
}
}
then the field x of class Point is no longer hidden within class Test;
instead, the simple name x now refers to the field Point.x. Code in class
Test may still refer to that same field as super.x. Therefore, the output
from this variant program is:
2 2
To answer Question 2
For case 2 if the servlet is unsyncronized then there is generally only one
instance and there are multiple threads running through it, one per
concurrent request.
For case 1 the servlet specification does specify exactly how the
SingleThreadModel should be implemented, and it will behave differently in
different servlet containers. I also have haeard and read that it is going
to be removed from the servlet specification in the future and in general
its use strongly discurouged.
To answer Question 3
An inner class has all the rights its "outer" or containing class has. Hence
the two inner classes may call each others private methods because the
containing class is allowed to. If you consider that access mofiers are
provided so that you can limit what "other" programmers (actually other
classes, you should consider yourself as a different programmer when coding
another class) can access, and if you acknowledge that a class, including
inner classes, is generally only written by one programer then it is
sensible that they can access each others private methods. Otherwise you
would just be hiding things from yourself.
Cheers
Adrian
> -----Original Message-----
> From: purushottam krishna hegde [SMTP:[EMAIL PROTECTED]
> Sent: 11 July 2003 07:08
> To: [EMAIL PROTECTED]
> Subject: private access specifier
>
> hi all,
> there r couple of of questions.
> Question 1)
> here is one interview question.
>
> Can u override variables?
> pl explain
> Question 2)can anybody explain me how a servlet containerhandles
> multiple request from diff clients when
> case a)there is only one instance in pool and there r 1000 requests
> sub case1: if servlet method is synchronised.(SingleThreadModel
> interface)
> sub case2: non synchronised service
>
> case b)there r 100 instance of servlet in pool and 1000 requests and
> non synchronised service
>
> as wrox book says
> it can adopt 2 methods.
> 1)instance pooling
> 2)request serialization
> bot for syn service method
> is this right?
>
>
> Question 3)
> here is some code which tests the private access specifiers class
> inner_one's constructor is private and one of its method is private it
> is still accessible by inner_two how?
> is private access specifier does't apply to inner classes?
> public class private_test{
> public class inner_one{
> private inner_one(){
> }
> private void inner_amethod(){
> }
> }
> public class inner_two{
> inner_two(){
> inner_one in1 = new inner_one();
> in1.inner_amethod();
> }
> }
> }
>
>
> _____
>
> Do you Yahoo!?
> SBC Yahoo! DSL
> <http://pa.yahoo.com/*http://rd.yahoo.com/evt=1207/*http://promo.yahoo
> .com
> /sbc/> - Now only $29.95 per month!
--
It is the strict policy of Truworths that its e-mail facility and all e-mail
communications emanating therefrom, should be utilised for business purposes
only and should conform to high professional and
business standards. Truworths has stipulated certain regulations in
terms whereof strict guidelines relating to the use and content of e-mail
communications are laid down. The use of the Truworths e-mail facility is
not permitted for the distribution of chain letters or
offensive mail of any nature whatsoever. Truworths hereby distances
itself from and accepts no liability in respect of the unauthorised use of
its e-mail facility or the sending of e-mail communications
for other than strictly business purposes. Truworths furthermore
disclaims liability for any unauthorised instruction for which
permission was not granted. Truworths Limited accepts no liability
for any consequences arising from or as a result of reliance on this message
unless it is in respect of bona fide Truworths business for which proper
authorisation has been granted.
Any recipient of an unacceptable communication, a chain letter or offensive
material of any nature is requested to notify the Truworths e-mail
administrator ([EMAIL PROTECTED]) immediately in order that appropriate
action can be taken against the individual concerned.
___________________________________________________________________________
To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
of the message "signoff SERVLET-INTEREST".
Archives: http://archives.java.sun.com/archives/servlet-interest.html
Resources: http://java.sun.com/products/servlet/external-resources.html
LISTSERV Help: http://www.lsoft.com/manuals/user/user.html
___________________________________________________________________________
To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
of the message "signoff SERVLET-INTEREST".
Archives: http://archives.java.sun.com/archives/servlet-interest.html
Resources: http://java.sun.com/products/servlet/external-resources.html
LISTSERV Help: http://www.lsoft.com/manuals/user/user.html
