An error keeps occurring for me that has been happening ever since I both installed a large number of plugins and updated JOSM at the same time.

[anonymous]

What steps will reproduce the problem?

What is the expected result?

What happens instead?

Please provide any additional information below. Attach a screenshot if possible.

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2018-08-18 16:16:51 +0200 (Sat, 18 Aug 2018)
Revision:14163
Build-Date:2018-08-18 16:30:21
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (14163 en) Windows 7 64-Bit
OS Build number: Windows 7 Professional (7601)
Memory Usage: 450 MB / 2020 MB (108 MB allocated, but free)
Java version: 9.0.1+11, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: \Display0 1600x900
Maximum Screen Size: 1600x900

Plugins:
+ CADTools (1007)
+ CustomizePublicTransportStop (34206)
+ FastDraw (34389)
+ FixAddresses (34389)
+ MicrosoftStreetside (1529284449)
+ MovementAlert (1509877002)
+ OpeningHoursEditor (34389)
+ PicLayer (34389)
+ ShapeTools (1230)
+ apache-commons (34506)
+ apache-http (34506)
+ buildings_tools (34212)
+ canvec_helper (34098)
+ conflation (0.6.0)
+ contourmerge (1012)
+ download_along (34389)
+ ejml (34389)
+ geojson (87)
+ geotools (34513)
+ indoorhelper (34389)
+ jts (34524)
+ merge-overlap (34389)
+ opendata (34389)
+ public_transport (34265)
+ reverter (34271)
+ rex (1529698495)
+ tageditor (34109)
+ terracer (34109)
+ turnlanes-tagging (263)
+ utilsplugin2 (34389)

Map paint styles:
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/LitObjects&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/LessObtrusiveNodes&zip=1
- https://josm.openstreetmap.de/josmfile?page=Styles/NewHighwayColors&zip=1
- <josm.pref>\styles\sit.mapcss

Validator rules:
+ <josm.pref>\validator\indoorhelper.validator.mapcss

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.
- E: java.util.concurrent.ExecutionException: java.lang.IncompatibleClassChangeError: Expecting non-static method org.openstreetmap.josm.data.Preferences.getAllPossiblePreferenceDirs()Ljava/util/Collection;. Cause: java.lang.IncompatibleClassChangeError: Expecting non-static method org.openstreetmap.josm.data.Preferences.getAllPossiblePreferenceDirs()Ljava/util/Collection;
- E: Handled by bug report queue: org.openstreetmap.josm.plugins.PluginException: An error occurred in plugin contourmerge. Cause: java.lang.NoClassDefFoundError: org/openstreetmap/josm/gui/MapView$LayerChangeListener. Cause: java.lang.ClassNotFoundException: org.openstreetmap.josm.gui.MapView$LayerChangeListener


=== REPORTED CRASH DATA ===
BugReportExceptionHandler#handleException:
No data collected.

Warning issued by: BugReportExceptionHandler#handleException

=== STACK TRACE ===
Thread: AWT-EventQueue-0 (21) of main
org.openstreetmap.josm.plugins.PluginException: An error occurred in plugin contourmerge
	at org.openstreetmap.josm.plugins.PluginProxy.handlePluginException(PluginProxy.java:60)
	at org.openstreetmap.josm.plugins.PluginProxy.addDownloadSelection(PluginProxy.java:97)
	at org.openstreetmap.josm.plugins.PluginHandler.addDownloadSelection(PluginHandler.java:1226)
	at org.openstreetmap.josm.gui.download.DownloadDialog.buildMainPanel(DownloadDialog.java:136)
	at org.openstreetmap.josm.gui.download.DownloadDialog.<init>(DownloadDialog.java:232)
	at org.openstreetmap.josm.gui.download.DownloadDialog.<init>(DownloadDialog.java:220)
	at org.openstreetmap.josm.gui.download.DownloadDialog.getInstance(DownloadDialog.java:82)
	at org.openstreetmap.josm.actions.DownloadAction.actionPerformed(DownloadAction.java:35)
	at java.desktop/javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
	at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
	at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
	at java.desktop/javax.swing.DefaultButtonModel.setPressed(Unknown Source)
	at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
	at java.desktop/java.awt.AWTEventMulticaster.mouseReleased(Unknown Source)
	at java.desktop/java.awt.Component.processMouseEvent(Unknown Source)
	at java.desktop/javax.swing.JComponent.processMouseEvent(Unknown Source)
	at java.desktop/java.awt.Component.processEvent(Unknown Source)
	at java.desktop/java.awt.Container.processEvent(Unknown Source)
	at java.desktop/java.awt.Component.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.Component.dispatchEvent(Unknown Source)
	at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
	at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
	at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
	at java.desktop/java.awt.Container.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.Window.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.Component.dispatchEvent(Unknown Source)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.EventQueue.access$500(Unknown Source)
	at java.desktop/java.awt.EventQueue$3.run(Unknown Source)
	at java.desktop/java.awt.EventQueue$3.run(Unknown Source)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.desktop/java.awt.EventQueue$4.run(Unknown Source)
	at java.desktop/java.awt.EventQueue$4.run(Unknown Source)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.desktop/java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.NoClassDefFoundError: org/openstreetmap/josm/gui/MapView$LayerChangeListener
	at java.base/java.lang.ClassLoader.defineClass1(Native Method)
	at java.base/java.lang.ClassLoader.defineClass(Unknown Source)
	at java.base/java.security.SecureClassLoader.defineClass(Unknown Source)
	at java.base/java.net.URLClassLoader.defineClass(Unknown Source)
	at java.base/java.net.URLClassLoader.access$100(Unknown Source)
	at java.base/java.net.URLClassLoader$1.run(Unknown Source)
	at java.base/java.net.URLClassLoader$1.run(Unknown Source)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at java.base/java.net.URLClassLoader.findClass(Unknown Source)
	at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
	at org.openstreetmap.josm.plugins.PluginClassLoader.loadClass(PluginClassLoader.java:74)
	at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
	at java.base/java.lang.Class.getDeclaredMethods0(Native Method)
	at java.base/java.lang.Class.privateGetDeclaredMethods(Unknown Source)
	at java.base/java.lang.Class.getMethodsRecursive(Unknown Source)
	at java.base/java.lang.Class.getMethod0(Unknown Source)
	at java.base/java.lang.Class.getMethod(Unknown Source)
	at org.openstreetmap.josm.plugins.PluginProxy.addDownloadSelection(PluginProxy.java:92)
	... 43 more
Caused by: java.lang.ClassNotFoundException: org.openstreetmap.josm.gui.MapView$LayerChangeListener
	at java.base/java.net.URLClassLoader.findClass(Unknown Source)
	at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
	at org.openstreetmap.josm.plugins.PluginClassLoader.loadClass(PluginClassLoader.java:74)
	at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
	... 61 more

[Don-vip]

Can you please try to:

• update to Java 10.0.2
• then update again your plugins

If you still get the error after that, please attach your new status report.