RFR: 8159055: ImageIcon.setImage and ImageIcon(Image) constructor can't handle null parameter [v10]

[Alexey Ivanov]

On Thu, 19 Jun 2025 03:01:15 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

>> When trying to call 'icon.setImage(null);' where 'icon' is an instance of ImageIcon, a null pointer exception is thrown at runtime.
>> The code tried to get the `id` for that image and instantiates `MediaTracker` to associate the null image to that `id` and checks the status of loading this null image, removes the null image from the tracker and then tries to get the image width where it throws NPE as image is null.
>> 
>> It's better to not go through all MediaTracker usage and bail out initially itself for null image..
>
> Prasanta Sadhukhan has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Test fix
>  - javadoc wording..clear image desscription if image is null

Changes requested by aivanov (Reviewer).

src/java.desktop/share/classes/javax/swing/ImageIcon.java line 147:

> 145:         image = Toolkit.getDefaultToolkit().getImage(filename);
> 146:         if (image == null) {
> 147:             this.description = null;

I do not think we have to enforce setting `description` to `null` if the image is `null` — **it is up to the developer to decide**.

src/java.desktop/share/classes/javax/swing/ImageIcon.java line 222:

> 220:      * Setting a {@code null} image means
> 221:      * any existing image will be removed
> 222:      * and no image will be rendered.

It doesn't apply to the constructor — there ***can't** be an existing image*!

src/java.desktop/share/classes/javax/swing/ImageIcon.java line 389:

> 387:         this.image = image;
> 388:         if (image == null) {
> 389:             this.description = null;

We must not change the description. Why do we enforce resetting the description to `null`?

The app is still free to change the description to an arbitrary value using `setDescription` even if the image is `null`.

src/java.desktop/share/classes/javax/swing/ImageIcon.java line 391:

> 389:             this.description = null;
> 390:             return;
> 391:         }

We must not change the description, but we should reset `width` and `height` to `-1`.
Suggestion:

            width = -1;
            height = -1;
            return;
        }

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

PR Review: https://git.openjdk.org/jdk/pull/25767#pullrequestreview-2942389792
PR Review Comment: https://git.openjdk.org/jdk/pull/25767#discussion_r2156647302
PR Review Comment: https://git.openjdk.org/jdk/pull/25767#discussion_r2156649370
PR Review Comment: https://git.openjdk.org/jdk/pull/25767#discussion_r2156652325
PR Review Comment: https://git.openjdk.org/jdk/pull/25767#discussion_r2156655243