RFR: 8159055: ImageIcon.setImage and ImageIcon(Image) constructor can't handle null parameter [v11]

[Alexey Ivanov]

On Fri, 20 Jun 2025 03:51:16 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 one additional commit since the last revision:
> 
>   Remove resetting description from constructor as it is already null

src/java.desktop/share/classes/javax/swing/ImageIcon.java line 233:

> 231:         Object o = image.getProperty("comment", imageObserver);
> 232:         if (o instanceof String) {
> 233:             description = (String) o;

To address [Phil's comment](https://github.com/openjdk/jdk/pull/25767/files#r2155610976):

> This is wasted work if the app calls ImageIcon(Image, String) because that promptly over-writes whatever was obtained via this code.

If we're going to change the constructors, to avoid *this wasted work* when `ImageIcon(Image, String)` constructor is called, I suggest moving the work into `ImageIcon(Image, String)` and implement `ImageIcon` like this:


    public ImageIcon (Image image) {
        String description = null;
        if (image != null) {
            Object o = image.getProperty("comment", null);
            if (o instanceof String) {
                description = (String) o;
            }
        }
        this(image, description);

It is allowed in JDK 22 and later.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25767#discussion_r2159249820