After JDK-8286447, 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)