JOSM won't start up on Kubuntu 24.04

[anonymous]

On a freshly installed Kubuntu 24.04, JOSM won't start up.

Java version is OpenJDK 21 from Ubuntu repos.

Starting manually from terminal gives the following response:

$ java --add-exports=java.base/sun.security.action=ALL-UNNAMED --add-exports=java.desktop/com.sun.imageio.plugins.jpeg=ALL-UNNAMED --add-exports=java.desktop/com.sun.imageio.spi=ALL-UNNAMED -jar /usr/share/josm/josm-1.5.svn19039.jar 
Picked up _JAVA_OPTIONS: -Dawt.useSystemAAFontSettings=lcd
2024-04-27 21:56:29.514 WARNUNG: COMPAT locale provider will be removed in a future release
2024-04-27 21:56:29.598 INFORMATION: Protokollierungsgrad ist bei INFORMATION (INFO, 800)
2024-04-27 21:56:30.031 INFORMATION: Nutzbares IPv6-Netzwerk erkannt, IPv6 wird gegenüber IPv4 bevorzugt.
2024-04-27 21:56:30.049 SCHWERWIEGEND: Handled by bug report queue: java.lang.NullPointerException: Cannot invoke "String.startsWith(String)" because "platName" is null
java.lang.NullPointerException: Cannot invoke "String.startsWith(String)" because "platName" is null
        at java.desktop/sun.awt.X11FontManager.getFileNameFromPlatformName(X11FontManager.java:161)
        at java.desktop/sun.font.SunFontManager.initCompositeFonts(SunFontManager.java:3102)
        at java.desktop/sun.font.SunFontManager$2.run(SunFontManager.java:445)
        at java.desktop/sun.font.SunFontManager$2.run(SunFontManager.java:309)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:319)
        at java.desktop/sun.font.SunFontManager.<init>(SunFontManager.java:309)
        at java.desktop/sun.awt.FcFontManager.<init>(FcFontManager.java:35)
        at java.desktop/sun.awt.X11FontManager.<init>(X11FontManager.java:55)
        at java.desktop/sun.font.PlatformFontInfo.createFontManager(PlatformFontInfo.java:37)
        at java.desktop/sun.font.FontManagerFactory.getInstance(FontManagerFactory.java:51)
        at java.desktop/sun.font.SunFontManager.getInstance(SunFontManager.java:242)
        at java.desktop/sun.font.FontDesignMetrics.getMetrics(FontDesignMetrics.java:260)
        at java.desktop/sun.swing.SwingUtilities2.getFontMetrics(SwingUtilities2.java:1242)
        at java.desktop/javax.swing.JComponent.getFontMetrics(JComponent.java:1700)
        at java.desktop/javax.swing.plaf.basic.BasicGraphicsUtils.getPreferredButtonSize(BasicGraphicsUtils.java:360)
        at java.desktop/javax.swing.plaf.basic.BasicButtonUI.getPreferredSize(BasicButtonUI.java:542)
        at java.desktop/javax.swing.plaf.basic.BasicButtonUI.getMinimumSize(BasicButtonUI.java:532)
        at java.desktop/javax.swing.JComponent.getMinimumSize(JComponent.java:1814)
        at java.desktop/javax.swing.plaf.basic.BasicOptionPaneUI.addButtonComponents(BasicOptionPaneUI.java:818)
        at java.desktop/javax.swing.plaf.basic.BasicOptionPaneUI.createButtonArea(BasicOptionPaneUI.java:751)
        at java.desktop/javax.swing.plaf.basic.BasicOptionPaneUI.installComponents(BasicOptionPaneUI.java:206)
        at java.desktop/javax.swing.plaf.basic.BasicOptionPaneUI.installUI(BasicOptionPaneUI.java:160)
        at java.desktop/javax.swing.JComponent.setUI(JComponent.java:740)
        at java.desktop/javax.swing.JOptionPane.setUI(JOptionPane.java:1858)
        at java.desktop/javax.swing.JOptionPane.updateUI(JOptionPane.java:1880)
        at java.desktop/javax.swing.JOptionPane.<init>(JOptionPane.java:1845)
        at java.desktop/javax.swing.JOptionPane.showOptionDialog(JOptionPane.java:869)
        at org.openstreetmap.josm.gui.MainApplication.mainJOSM(MainApplication.java:891)
        at org.openstreetmap.josm.gui.MainApplication$3.processArguments(MainApplication.java:285)
        at org.openstreetmap.josm.gui.MainApplication.main(MainApplication.java:788)

2024-04-27 21:56:31.373 SCHWERWIEGEND: Exception raised in EDT: java.util.concurrent.ExecutionException: java.lang.NullPointerException: Cannot invoke "String.startsWith(String)" because "platName" is null. Ursache: java.lang.NullPointerException: Cannot invoke "String.startsWith(String)" because "platName" is null
java.util.concurrent.ExecutionException: java.lang.NullPointerException: Cannot invoke "String.startsWith(String)" because "platName" is null
        at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
        at org.openstreetmap.josm.gui.util.GuiHelper.runInEDTAndWaitAndReturn(GuiHelper.java:278)
        at org.openstreetmap.josm.gui.bugreport.BugReportDialog.showFor(BugReportDialog.java:233)
        at org.openstreetmap.josm.tools.bugreport.BugReportQueue.displayFor(BugReportQueue.java:134)
        at org.openstreetmap.josm.tools.bugreport.BugReportQueue.access$200(BugReportQueue.java:17)
        at org.openstreetmap.josm.tools.bugreport.BugReportQueue$BugReportDisplayRunnable.run(BugReportQueue.java:100)
        at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: java.lang.NullPointerException: Cannot invoke "String.startsWith(String)" because "platName" is null
        at java.desktop/sun.awt.X11FontManager.getFileNameFromPlatformName(X11FontManager.java:161)
        at java.desktop/sun.font.SunFontManager.initCompositeFonts(SunFontManager.java:3102)
        at java.desktop/sun.font.SunFontManager$2.run(SunFontManager.java:445)
        at java.desktop/sun.font.SunFontManager$2.run(SunFontManager.java:309)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:319)
        at java.desktop/sun.font.SunFontManager.<init>(SunFontManager.java:309)
        at java.desktop/sun.awt.FcFontManager.<init>(FcFontManager.java:35)
        at java.desktop/sun.awt.X11FontManager.<init>(X11FontManager.java:55)
        at java.desktop/sun.font.PlatformFontInfo.createFontManager(PlatformFontInfo.java:37)
        at java.desktop/sun.font.FontManagerFactory.getInstance(FontManagerFactory.java:51)
        at java.desktop/sun.font.SunFontManager.getInstance(SunFontManager.java:242)
        at java.desktop/sun.font.FontDesignMetrics.getMetrics(FontDesignMetrics.java:260)
        at java.desktop/sun.swing.SwingUtilities2.getFontMetrics(SwingUtilities2.java:1242)
        at java.desktop/javax.swing.JComponent.getFontMetrics(JComponent.java:1700)
        at java.desktop/javax.swing.text.PlainView.calculateLongestLine(PlainView.java:783)
        at java.desktop/javax.swing.text.PlainView.updateMetrics(PlainView.java:332)
        at java.desktop/javax.swing.text.PlainView.updateDamage(PlainView.java:670)
        at java.desktop/javax.swing.text.PlainView.insertUpdate(PlainView.java:591)
        at java.desktop/javax.swing.plaf.basic.BasicTextUI$RootView.insertUpdate(BasicTextUI.java:1711)
        at java.desktop/javax.swing.plaf.basic.BasicTextUI$UpdateHandler.insertUpdate(BasicTextUI.java:1978)
        at java.desktop/javax.swing.text.AbstractDocument.fireInsertUpdate(AbstractDocument.java:227)
        at java.desktop/javax.swing.text.AbstractDocument.handleInsertString(AbstractDocument.java:781)
        at java.desktop/javax.swing.text.AbstractDocument.insertString(AbstractDocument.java:740)
        at java.desktop/javax.swing.text.PlainDocument.insertString(PlainDocument.java:131)
        at java.desktop/javax.swing.text.AbstractDocument.replace(AbstractDocument.java:699)
        at java.desktop/javax.swing.text.JTextComponent.setText(JTextComponent.java:1725)
        at org.openstreetmap.josm.gui.bugreport.DebugTextDisplay.setCodeText(DebugTextDisplay.java:62)
        at org.openstreetmap.josm.gui.bugreport.DebugTextDisplay.<init>(DebugTextDisplay.java:52)
        at org.openstreetmap.josm.gui.bugreport.BugReportDialog.<init>(BugReportDialog.java:62)
        at org.openstreetmap.josm.gui.bugreport.BugReportDialog.lambda$showFor$3(BugReportDialog.java:242)
        at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
        at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:318)
        at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:773)
        at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:720)
        at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:714)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
        at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87)
        at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
        at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
        at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
        at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
        at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
        at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
        at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

... then the terminal freezes (until I hit Ctrl-C).

[GerdP]

See also ​https://community.openstreetmap.org/t/josm-und-kubuntu-24-04/112406

[stoecker]

The error comes from a code section which will tell you, that JOSM couldn't start multiple times. Something is seriously broken. Did you clean all JOSM data as well (.config, .cache and so on?). Do other java applications with a GUI start?

[GerdP]

See discussion. It seems the user updated only a part of the system to Kubuntu 24.04, the rest was 23.10.