Re: checking for null Noob question
I won't do the second one because you could see a NullPointerException. Is it
your question ?
Jérémy
Le 31 juil. 2010 à 14:05, Theodore Petrosky a écrit :
Why does this work:
public String dueDateTypeLetter() {
if (this.dueDateType() == null || this.dueDateType().equals(N)) {
return ;
}
return this.dueDateType();
}
and this doesn't
public String dueDateTypeLetter() {
if (this.dueDateType().equals(N) || this.dueDateType() == null) {
return ;
}
return this.dueDateType();
}
obviously the difference is the order of checking in the 'if' statement...
I don't really care that I must check in a specific order... It just took me
time to understand that the order was important.
Ted
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/jeremy.deroyer%40ingencys.net
This email sent to jeremy.dero...@ingencys.net
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
Re: checking for null Noob question
Yes... I was asking 'Why?' is there a NullPointerException with number 2...
Ted
--- On Sat, 7/31/10, Jérémy DE ROYER jeremy.dero...@ingencys.net wrote:
From: Jérémy DE ROYER jeremy.dero...@ingencys.net
Subject: Re: checking for null Noob question
To: Theodore Petrosky tedp...@yahoo.com
Cc: webobjects-dev@lists.apple.com
Date: Saturday, July 31, 2010, 8:07 AM
I won't do the second one because you
could see a NullPointerException. Is it your question ?
Jérémy
Le 31 juil. 2010 à 14:05, Theodore Petrosky a écrit :
Why does this work:
public String dueDateTypeLetter() {
if (this.dueDateType() == null ||
this.dueDateType().equals(N)) {
return ;
}
return this.dueDateType();
}
and this doesn't
public String dueDateTypeLetter() {
if (this.dueDateType().equals(N) ||
this.dueDateType() == null) {
return ;
}
return this.dueDateType();
}
obviously the difference is the order of checking in
the 'if' statement...
I don't really care that I must check in a specific
order... It just took me time to understand that the order
was important.
Ted
___
Do not post admin requests to the list. They will be
ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/jeremy.deroyer%40ingencys.net
This email sent to jeremy.dero...@ingencys.net
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
Re: checking for null Noob question
So the answer is :
- if the object is null, as, in the second test, your use the method 'equals'
on this object (null) NullPointerException
On the first test, as you first test if the object is null, you can't have a
NullPointerException
Hope this help,
Jérémy
Le 31 juil. 2010 à 14:09, Theodore Petrosky a écrit :
Yes... I was asking 'Why?' is there a NullPointerException with number 2...
Ted
--- On Sat, 7/31/10, Jérémy DE ROYER jeremy.dero...@ingencys.net wrote:
From: Jérémy DE ROYER jeremy.dero...@ingencys.net
Subject: Re: checking for null Noob question
To: Theodore Petrosky tedp...@yahoo.com
Cc: webobjects-dev@lists.apple.com
Date: Saturday, July 31, 2010, 8:07 AM
I won't do the second one because you
could see a NullPointerException. Is it your question ?
Jérémy
Le 31 juil. 2010 à 14:05, Theodore Petrosky a écrit :
Why does this work:
public String dueDateTypeLetter() {
if (this.dueDateType() == null ||
this.dueDateType().equals(N)) {
return ;
}
return this.dueDateType();
}
and this doesn't
public String dueDateTypeLetter() {
if (this.dueDateType().equals(N) ||
this.dueDateType() == null) {
return ;
}
return this.dueDateType();
}
obviously the difference is the order of checking in
the 'if' statement...
I don't really care that I must check in a specific
order... It just took me time to understand that the order
was important.
Ted
___
Do not post admin requests to the list. They will be
ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/jeremy.deroyer%40ingencys.net
This email sent to jeremy.dero...@ingencys.net
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
Re: checking for null Noob question
Or do the following trick:
if(!N.equals(this.dueDateType()) {
return this.dueDateType();
}
return ;
Or failsafe operation:
if(!(this.dueDateType()+).equals(N)) {
return this.dueDateType();
}
return ;
But all above are applicable to strings only. For other types, you always need
to follow the LTR precedence.
Or use try-catch-finally block. Do the wrong things in try, fix the wrong in
catch and use finally for final work. ;)
Farrukh
Sent from my iPad
On 31-Jul-2010, at 3:13 PM, Jérémy DE ROYER jeremy.dero...@ingencys.net wrote:
So the answer is :
- if the object is null, as, in the second test, your use the method
'equals' on this object (null) NullPointerException
On the first test, as you first test if the object is null, you can't have a
NullPointerException
Hope this help,
Jérémy
Le 31 juil. 2010 à 14:09, Theodore Petrosky a écrit :
Yes... I was asking 'Why?' is there a NullPointerException with number 2...
Ted
--- On Sat, 7/31/10, Jérémy DE ROYER jeremy.dero...@ingencys.net wrote:
From: Jérémy DE ROYER jeremy.dero...@ingencys.net
Subject: Re: checking for null Noob question
To: Theodore Petrosky tedp...@yahoo.com
Cc: webobjects-dev@lists.apple.com
Date: Saturday, July 31, 2010, 8:07 AM
I won't do the second one because you
could see a NullPointerException. Is it your question ?
Jérémy
Le 31 juil. 2010 à 14:05, Theodore Petrosky a écrit :
Why does this work:
public String dueDateTypeLetter() {
if (this.dueDateType() == null ||
this.dueDateType().equals(N)) {
return ;
}
return this.dueDateType();
}
and this doesn't
public String dueDateTypeLetter() {
if (this.dueDateType().equals(N) ||
this.dueDateType() == null) {
return ;
}
return this.dueDateType();
}
obviously the difference is the order of checking in
the 'if' statement...
I don't really care that I must check in a specific
order... It just took me time to understand that the order
was important.
Ted
___
Do not post admin requests to the list. They will be
ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/jeremy.deroyer%40ingencys.net
This email sent to jeremy.dero...@ingencys.net
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/farrukh.ijaz%40fuegodigitalmedia.com
This email sent to farrukh.i...@fuegodigitalmedia.com
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
Re: checking for null Noob question
Hi Ted,
The '||' operator is a 'short circuit' operator, and it evaluates the left-hand
side first. Assume this.dueDateType() returns null, then in this case:
On 31/07/2010, at 9:35 PM, Theodore Petrosky wrote:
if (this.dueDateType() == null || this.dueDateType().equals(N)) {
the expression on the left-hand side is true, and the right-hand side is never
evaluated (because its value won't affect the value of the whole expression).
That is, it short circuits and you avoid a NullPointerException. In this
case:
if (this.dueDateType().equals(N) || this.dueDateType() == null) {
this.dueDateType().equals(N) is evaluated, and you get a NullPointerException.
I don't really care that I must check in a specific order... It just took me
time to understand that the order was important.
The order is only important to the extent that the LHS is always evaluated, and
the RHS is only evaluated if the LHS is false. So in this case, where you're
doing a null check specifically to avoid an exception, yes it needs to be on
the LHS.
http://en.wikipedia.org/wiki/Short-circuit_evaluation
--
Paul.
http://logicsquad.net/
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
Re: checking for null Noob question
Thanks, this was exactly the information I was looking for.
Ted
--- On Sat, 7/31/10, Paul Hoadley pa...@logicsquad.net wrote:
From: Paul Hoadley pa...@logicsquad.net
Subject: Re: checking for null Noob question
To: Theodore Petrosky tedp...@yahoo.com
Cc: webobjects-dev@lists.apple.com
Date: Saturday, July 31, 2010, 8:46 AM
Hi Ted,
The '||' operator is a 'short circuit' operator, and it
evaluates the left-hand side first. Assume
this.dueDateType() returns null, then in this case:
On 31/07/2010, at 9:35 PM, Theodore Petrosky wrote:
if (this.dueDateType() == null ||
this.dueDateType().equals(N)) {
the expression on the left-hand side is true, and the
right-hand side is never evaluated (because its value won't
affect the value of the whole expression). That is, it
short circuits and you avoid a NullPointerException.
In this case:
if (this.dueDateType().equals(N) ||
this.dueDateType() == null) {
this.dueDateType().equals(N) is evaluated, and you get a
NullPointerException.
I don't really care that I must check in a specific
order... It just took me time to understand that the order
was important.
The order is only important to the extent that the LHS is
always evaluated, and the RHS is only evaluated if the LHS
is false. So in this case, where you're doing a null
check specifically to avoid an exception, yes it needs to be
on the LHS.
http://en.wikipedia.org/wiki/Short-circuit_evaluation
--
Paul.
http://logicsquad.net/
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
Re: checking for null Noob question
+1 for N.equals(whatever) to prevent NPEs
Sent from my iPhone
On Jul 31, 2010, at 9:44 AM, Theodore Petrosky tedp...@yahoo.com wrote:
Thanks, this was exactly the information I was looking for.
Ted
--- On Sat, 7/31/10, Paul Hoadley pa...@logicsquad.net wrote:
From: Paul Hoadley pa...@logicsquad.net
Subject: Re: checking for null Noob question
To: Theodore Petrosky tedp...@yahoo.com
Cc: webobjects-dev@lists.apple.com
Date: Saturday, July 31, 2010, 8:46 AM
Hi Ted,
The '||' operator is a 'short circuit' operator, and it
evaluates the left-hand side first. Assume
this.dueDateType() returns null, then in this case:
On 31/07/2010, at 9:35 PM, Theodore Petrosky wrote:
if (this.dueDateType() == null ||
this.dueDateType().equals(N)) {
the expression on the left-hand side is true, and the
right-hand side is never evaluated (because its value won't
affect the value of the whole expression). That is, it
short circuits and you avoid a NullPointerException.
In this case:
if (this.dueDateType().equals(N) ||
this.dueDateType() == null) {
this.dueDateType().equals(N) is evaluated, and you get a
NullPointerException.
I don't really care that I must check in a specific
order... It just took me time to understand that the order
was important.
The order is only important to the extent that the LHS is
always evaluated, and the RHS is only evaluated if the LHS
is false. So in this case, where you're doing a null
check specifically to avoid an exception, yes it needs to be
on the LHS.
http://en.wikipedia.org/wiki/Short-circuit_evaluation
--
Paul.
http://logicsquad.net/
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/mschrag%40pobox.com
This email sent to msch...@pobox.com
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
Re: checking for null Noob question
Just to avoid confusion and the NullPointerException, I would suggest this:
{
if (this.dueDateType() == null) {
return ;
}
else if (this.dueDateType().equals(N)) {
return ;
}
return this.dueDateType();
}
or this:
{
if (this.dueDateType() != null) {
if (!this.dueDateType().equals(N)) {
return this.dueDateType();
}
}
return ;
}
Steve
On Jul 31, 2010, at 8:13 AM, Jérémy DE ROYER wrote:
So the answer is :
- if the object is null, as, in the second test, your use the method
'equals' on this object (null) NullPointerException
On the first test, as you first test if the object is null, you can't have a
NullPointerException
Hope this help,
Jérémy
Le 31 juil. 2010 à 14:09, Theodore Petrosky a écrit :
Yes... I was asking 'Why?' is there a NullPointerException with number 2...
Ted
--- On Sat, 7/31/10, Jérémy DE ROYER jeremy.dero...@ingencys.net wrote:
From: Jérémy DE ROYER jeremy.dero...@ingencys.net
Subject: Re: checking for null Noob question
To: Theodore Petrosky tedp...@yahoo.com
Cc: webobjects-dev@lists.apple.com
Date: Saturday, July 31, 2010, 8:07 AM
I won't do the second one because you
could see a NullPointerException. Is it your question ?
Jérémy
Le 31 juil. 2010 à 14:05, Theodore Petrosky a écrit :
Why does this work:
public String dueDateTypeLetter() {
if (this.dueDateType() == null ||
this.dueDateType().equals(N)) {
return ;
}
return this.dueDateType();
}
and this doesn't
public String dueDateTypeLetter() {
if (this.dueDateType().equals(N) ||
this.dueDateType() == null) {
return ;
}
return this.dueDateType();
}
obviously the difference is the order of checking in
the 'if' statement...
I don't really care that I must check in a specific
order... It just took me time to understand that the order
was important.
Ted
___
Do not post admin requests to the list. They will be
ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/jeremy.deroyer%40ingencys.net
This email sent to jeremy.dero...@ingencys.net
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/speery%40me.com
This email sent to spe...@me.com
___
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (Webobjects-dev@lists.apple.com)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/webobjects-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
