Re: [platform-ui-dev] arrays and generics in JFace

[Markus Keller <markus_keller@xxxxxxxxxx>]

The right solution for array creations
with a variable type is to use @SuppressWarnings("unchecked")
on the smallest element possible.

Introduce a local variable to avoid
marking the whole method as unchecked. If you have to use the same pattern
in many places, then extract it into a method (but only if you can guarantee
that this won't hide actual ClassCastExceptions at run time).

The second proposed solution with the
additional ArrayList only suppressed the warning by accident. I just fixed
https://bugs.eclipse.org/338350
so that casting to (E[]) will always show the warning, even when the "Ignore
unavoidable generic type problems" compiler option is enabled. And
BTW: creating an additional object just to suppress a warning is always
wrong.

Markus



From:      
 Daniel Megert/Zurich/IBM@IBMCH
To:      
 "Eclipse Platform
UI component developers list." <platform-ui-dev@xxxxxxxxxxx>
Date:      
 2013-07-29 10:46
Subject:    
   Re: [platform-ui-dev]
arrays and generics in JFace
Sent by:    
   platform-ui-dev-bounces@xxxxxxxxxxx

---

> Based on an
offline discussion with John, I think @SuppressWarning is the better approach
as this avoid the unnecessary object creation. 

If the method is not called extensively, then that object creation is negligible
in my opinion and "clean" code preferred. Also note that the
proposed code does not compiled as is: you would either have to add a local
variable or move the @SuppressWarnings to the method.

Dani 


From:        Lars
Vogel <lars.vogel@xxxxxxxxx> 
To:        "Eclipse
Platform UI component developers list." <platform-ui-dev@xxxxxxxxxxx>
Date:        26.07.2013
20:23 
Subject:        Re:
[platform-ui-dev] arrays and generics in JFace 
Sent by:        platform-ui-dev-bounces@xxxxxxxxxxx

---

Based on an offline discussion with John, I think @SuppressWarning is the
better approach as this avoid the unnecessary object creation. 

Best regards, Lars 

Am Freitag, 26. Juli 2013 schrieb Hendrik Still : 
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi,
I'm currently adding generics support to the JFace Viewer. But run
into problems with the generic typisation of mostly object typed
arrays. I know arrays and generics do not mix very well. But I'm not
able to replace arrays by lists, because this would break the
compatibility top older versions.

But how should I type/cast the arrays correctly?

Here is an example from the
org.eclipse.jface.viewers.LabelProviderChangedEvent Classe:
- ------------------------------------------------------------

private Object[] elements;
//...
    public LabelProviderChangedEvent(IBaseLabelProvider source,
Object
element) {
        super(source);
        this.elements = new Object[1];
        this.elements[0] = element;
    }

- ------------------------------------------------------------

First solution would be this:
- ------------------------------------------------------------
private E[] elements;
//...
    public LabelProviderChangedEvent(IBaseLabelProvider<E>
source, E
element) {
        super(source);
        @SuppressWarnings("unchecked")
        this.elements = (E[]) new Object[1]; //Warning
        this.elements[0] = element;
    }
- ------------------------------------------------------------

Second would be this:
- ------------------------------------------------------------
public LabelProviderChangedEvent(IBaseLabelProvider<E> source, E
element) {
        super(source);
        ArrayList<E> arrayList = new ArrayList<E>();
        arrayList.add(element);
        this.elements = (E[]) arrayList.toArray();
    }
- ------------------------------------------------------------

What do you think is the better solution in the case of the JFace
Toolkit? Or do you have a better idea to solve this problem?

Regars,
Hendrik


-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (GNU/Linux)
Comment: Using GnuPG with undefined - http://www.enigmail.net/

iQEcBAEBAgAGBQJR8aWwAAoJECjZOs4dIxisZh0IAK+DqsNioocPTvJIRBdLfX8z
J6SCJO2rVuCFjZLO+yRxBxnELRspWCMISPwgMCRgzlCHiajWqD9SqectqNCMQhIb
3xkR7zOaInsQzpF/u6DLUEFdcSzpUDSOU2dEC+9SGhki2Ic79py5QBUFOYSCvfNm
BogYwXKkjbdN7E2XipGvYHOsgJjq+TXKXs5w4E9d/EsHR0R+rm4LyZ+eP5PtXr/X
S/U7UMC/ND8gwabIqprlX4Sp2OYfkxCrQtxiGbmPOEDoEtWzNaMlzhCpZsHut8VO
bdRL0+cynZVcI67WL6GDjCE76twNV/pp3fCrr3OCYGN4u+4n8xWDViaWkGLMi14=
=LYpj
-----END PGP SIGNATURE-----
_______________________________________________
platform-ui-dev mailing list
platform-ui-dev@xxxxxxxxxxx
https://dev.eclipse.org/mailman/listinfo/platform-ui-dev_______________________________________________
platform-ui-dev mailing list
platform-ui-dev@xxxxxxxxxxx
https://dev.eclipse.org/mailman/listinfo/platform-ui-dev
_______________________________________________
platform-ui-dev mailing list
platform-ui-dev@xxxxxxxxxxx
https://dev.eclipse.org/mailman/listinfo/platform-ui-dev