RFR: 8357675: Amend headless message

[Phil Race]

On Mon, 26 May 2025 16:38:21 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

> Currently, the default headless message ends with a comma instead of full stop and has an additional line break.
> 
> 
> Exception in thread "AWT-EventQueue-0" java.awt.HeadlessException:
> No X11 DISPLAY variable was set,
> or no headful library support was found,
> but this program performed an operation which requires it,
> 
>         at java.desktop/java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:158)
>         at java.desktop/java.awt.Window.<init>(Window.java:518)
>         at java.desktop/java.awt.Frame.<init>(Frame.java:428)
>         at java.desktop/javax.swing.JFrame.<init>(JFrame.java:224) 
> 
> 
> **Fix:**
> 
> Amend the message so that it ends with a full stop and remove the line break.
> 
> 
> Exception in thread "AWT-EventQueue-0" java.awt.HeadlessException:
> No X11 DISPLAY variable was set,
> or no headful library support was found,
> but this program performed an operation which requires it.
>         at java.desktop/java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:158)
>         at java.desktop/java.awt.Window.<init>(Window.java:518)
>         at java.desktop/java.awt.Frame.<init>(Frame.java:428)
>         at java.desktop/javax.swing.JFrame.<init>(JFrame.java:224)
> 
> 
> **Testing:**
> 
> Build a headless-only JDK (pass `--enable-headless-only` to the `configure` script) and create a `JFrame`.
> 
> It's impossible to create an automated test for this change, and I don't think a test is required, it's a cosmetic change.

The existing message is fine. The comma is because it isn't done. It introduces the exception text and the blank line adds some clarity. So nothing to change here.

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

PR Comment: https://git.openjdk.org/jdk/pull/25453#issuecomment-2910292746