Well If we're talking about the 'Enhanced For loop' in Java from 1.5 onwards
Then it goes something like this, you'll only get NPE if you haven't
initialized the collection,
otherwise if you've initialized the collection and there are no values in it
then
the for loop won't execute any iteration.
For example :
import java.util.ArrayList;
class Test{
static ArrayList<String>t;
public static void main(String [] args){
System.out.println("before===========");
for(String k : t){
System.out.println("===="+k);
}
System.out.println("after===========");
}
}
The above program will generate an NPE when ran and the output will be :
before===========
Exception in thread "main" java.lang.NullPointerException
at Test.main(Test.java:11)
but if I replace the ArrayList declaration with :
static ArrayList<String> t = new ArrayList<String>();
then the output will be :
before===========
after===========
Hope this helps.
Regards
Prince
________________________________
From: Paul Foxworthy <p...@cohsoft.com.au>
To: dev@ofbiz.apache.org
Sent: Tuesday, March 20, 2012 4:17 PM
Subject: Re: loop code simplification
Hi Erwan,
To be sure there is no Null Pointer Exception, yes, you need to test for
null first. One possibility is to just let the NPE happen.
The discussion at
http://stackoverflow.com/questions/2250031/null-check-in-an-enhanced-for-loop
suggests
for( Object o : safe( list ) ) {
// do whatever
}
Where safe would be:
public static List safe( List other ) {
return other == null ? Collections.EMPTY_LIST : other;
}
Cleaner code. I suspect the method would be inlined by most Java compilers.
Cheers
Paul Foxworthy
Erwan de FERRIERES-3 wrote
>
> Hi,
>
> I'm trying to remove a lot of iterators, and use the for-each syntax,
> which exists since java 1.5.
> During my journey, I found a lot of double tests for a while like this
> one:
>
> while (typePurposes != null && typePurposes.hasNext()) {
> (ContactMechWorker.java line 606)
>
> Can it be simplified to for(GenericValue contactMechTypePurpose :
> theList) ? Or should I keep it like it is ?
>
> Regards,
>
> --
> Erwan de FERRIERES
> www.nereide.biz
>
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