0

Short Version:

  • Couldn't start eclipse
  • Deleted some snap and tree files
  • Can open eclipse but it can't find my files “Cannot determine URI for [project-name]/[file-path]/[file-name]”
  • Can't reimport them as Eclipse is unable to recognize .java files

Long Version: It all started with this Error message this morning (took the latest one):

!SESSION 2020-11-26 10:13:32.039 -----------------------------------------------
eclipse.buildId=4.17.0.I20200902-1800
java.version=14.0.2
java.vendor=Oracle Corporation
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=de_DE
Framework arguments:  -product org.eclipse.epp.package.java.product
Command-line arguments:  -os win32 -ws win32 -arch x86_64 -product org.eclipse.epp.package.java.product

!ENTRY org.eclipse.oomph.util 4 0 2020-11-26 10:13:33.112
!MESSAGE FrameworkEvent ERROR
!STACK 0
org.osgi.framework.BundleException: Could not resolve module: org.eclipse.oomph.util [879]
  Another singleton bundle selected: osgi.identity; type="osgi.bundle"; version:Version="1.16.0.v20200917-0735"; osgi.identity="org.eclipse.oomph.util"; singleton:="true"

    at org.eclipse.osgi.container.Module.start(Module.java:463)
    at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel$2.run(ModuleContainer.java:1845)
    at org.eclipse.osgi.internal.framework.EquinoxContainerAdaptor$1$1.execute(EquinoxContainerAdaptor.java:136)
    at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.incStartLevel(ModuleContainer.java:1838)
    at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.incStartLevel(ModuleContainer.java:1779)
    at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.doContainerStartLevel(ModuleContainer.java:1743)
    at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.dispatchEvent(ModuleContainer.java:1665)
    at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.dispatchEvent(ModuleContainer.java:1)
    at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:234)
    at org.eclipse.osgi.framework.eventmgr.EventManager$EventThread.run(EventManager.java:345)

!ENTRY org.eclipse.core.resources 2 10035 2020-11-26 10:13:44.879
!MESSAGE The workspace exited with unsaved changes in the previous session; refreshing workspace to recover changes.

!ENTRY org.apache.felix.scr 4 0 2020-11-26 10:13:44.894
!MESSAGE bundle org.apache.felix.scr:2.1.16.v20200110-1820 (552)Error while disposing components of bundle org.eclipse.core.resources:3.13.800.v20200706-2152 (591)
!STACK 0
java.lang.IllegalStateException: BundleContext is no longer valid org.eclipse.core.resources_3.13.800.v20200706-2152 [591]
    at org.eclipse.osgi.internal.framework.BundleContextImpl.checkValid(BundleContextImpl.java:1027)
    at org.eclipse.osgi.internal.framework.BundleContextImpl.ungetService(BundleContextImpl.java:697)
    at org.apache.felix.scr.impl.logger.LogServiceEnabledLogger$1.removedService(LogServiceEnabledLogger.java:79)
    at org.osgi.util.tracker.ServiceTracker$Tracked.customizerRemoved(ServiceTracker.java:969)
    at org.osgi.util.tracker.ServiceTracker$Tracked.customizerRemoved(ServiceTracker.java:1)
    at org.osgi.util.tracker.AbstractTracked.untrack(AbstractTracked.java:341)
    at org.osgi.util.tracker.ServiceTracker.close(ServiceTracker.java:380)
    at org.apache.felix.scr.impl.logger.LogServiceEnabledLogger.close(LogServiceEnabledLogger.java:91)
    at org.apache.felix.scr.impl.logger.BundleLogger.close(BundleLogger.java:28)
    at org.apache.felix.scr.impl.BundleComponentActivator.dispose(BundleComponentActivator.java:531)
    at org.apache.felix.scr.impl.Activator.disposeComponents(Activator.java:429)
    at org.apache.felix.scr.impl.Activator.access$300(Activator.java:49)
    at org.apache.felix.scr.impl.Activator$ScrExtension.destroy(Activator.java:292)
    at org.apache.felix.scr.impl.AbstractExtender$1.run(AbstractExtender.java:216)
    at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at org.apache.felix.scr.impl.AbstractExtender.destroyExtension(AbstractExtender.java:238)
    at org.apache.felix.scr.impl.AbstractExtender.bundleChanged(AbstractExtender.java:132)
    at org.eclipse.osgi.internal.framework.BundleContextImpl.dispatchEvent(BundleContextImpl.java:945)
    at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:234)
    at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:151)
    at org.eclipse.osgi.internal.framework.EquinoxEventPublisher.publishBundleEventPrivileged(EquinoxEventPublisher.java:232)
    at org.eclipse.osgi.internal.framework.EquinoxEventPublisher.publishBundleEvent(EquinoxEventPublisher.java:138)
    at org.eclipse.osgi.internal.framework.EquinoxEventPublisher.publishBundleEvent(EquinoxEventPublisher.java:130)
    at org.eclipse.osgi.internal.framework.EquinoxContainerAdaptor.publishModuleEvent(EquinoxContainerAdaptor.java:217)
    at org.eclipse.osgi.container.Module.publishEvent(Module.java:499)
    at org.eclipse.osgi.container.Module.doStart(Module.java:611)
    at org.eclipse.osgi.container.Module.start(Module.java:468)
    at org.eclipse.osgi.framework.util.SecureAction.start(SecureAction.java:506)
    at org.eclipse.osgi.internal.hooks.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:117)
    at org.eclipse.osgi.internal.loader.classpath.ClasspathManager.findLocalClass(ClasspathManager.java:572)
    at org.eclipse.osgi.internal.loader.ModuleClassLoader.findLocalClass(ModuleClassLoader.java:346)
    at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:398)
    at org.eclipse.osgi.internal.loader.sources.SingleSourcePackage.loadClass(SingleSourcePackage.java:41)
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:473)
    at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:171)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:151)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:657)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:594)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1465)

!ENTRY org.eclipse.osgi 4 0 2020-11-26 10:13:44.894
!MESSAGE An error occurred while automatically activating bundle org.eclipse.core.resources (591).
!STACK 0
org.osgi.framework.BundleException: Exception in org.eclipse.core.resources.ResourcesPlugin.start() of bundle org.eclipse.core.resources.
    at org.eclipse.osgi.internal.framework.BundleContextImpl.startActivator(BundleContextImpl.java:835)
    at org.eclipse.osgi.internal.framework.BundleContextImpl.start(BundleContextImpl.java:763)
    at org.eclipse.osgi.internal.framework.EquinoxBundle.startWorker0(EquinoxBundle.java:1011)
    at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.startWorker(EquinoxBundle.java:365)
    at org.eclipse.osgi.container.Module.doStart(Module.java:605)
    at org.eclipse.osgi.container.Module.start(Module.java:468)
    at org.eclipse.osgi.framework.util.SecureAction.start(SecureAction.java:506)
    at org.eclipse.osgi.internal.hooks.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:117)
    at org.eclipse.osgi.internal.loader.classpath.ClasspathManager.findLocalClass(ClasspathManager.java:572)
    at org.eclipse.osgi.internal.loader.ModuleClassLoader.findLocalClass(ModuleClassLoader.java:346)
    at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:398)
    at org.eclipse.osgi.internal.loader.sources.SingleSourcePackage.loadClass(SingleSourcePackage.java:41)
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:473)
    at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:171)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:151)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:657)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:594)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1465)
Caused by: org.eclipse.core.internal.dtree.ObjectNotFoundException: Tree element '/04-HA-Advanced-StopWatch-Muster/src/idh/java/ha/StopWatch.java' not found.
    at org.eclipse.core.internal.dtree.AbstractDataTree.handleNotFound(AbstractDataTree.java:260)
    at org.eclipse.core.internal.dtree.DeltaDataTree.getData(DeltaDataTree.java:599)
    at org.eclipse.core.internal.dtree.DataDeltaNode.asBackwardDelta(DataDeltaNode.java:54)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.DataDeltaNode.asBackwardDelta(DataDeltaNode.java:51)
    at org.eclipse.core.internal.dtree.DeltaDataTree.asBackwardDelta(DeltaDataTree.java:91)
    at org.eclipse.core.internal.dtree.DeltaDataTree.reroot(DeltaDataTree.java:835)
    at org.eclipse.core.internal.dtree.DeltaDataTree.reroot(DeltaDataTree.java:834)
    at org.eclipse.core.internal.dtree.DeltaDataTree.reroot(DeltaDataTree.java:811)
    at org.eclipse.core.internal.watson.ElementTree.immutable(ElementTree.java:522)
    at org.eclipse.core.internal.resources.SaveManager.restore(SaveManager.java:731)
    at org.eclipse.core.internal.resources.SaveManager.startup(SaveManager.java:1555)
    at org.eclipse.core.internal.resources.Workspace.startup(Workspace.java:2452)
    at org.eclipse.core.internal.resources.Workspace.open(Workspace.java:2210)
    at org.eclipse.core.resources.ResourcesPlugin.start(ResourcesPlugin.java:489)
    at org.eclipse.osgi.internal.framework.BundleContextImpl$2.run(BundleContextImpl.java:814)
    at org.eclipse.osgi.internal.framework.BundleContextImpl$2.run(BundleContextImpl.java:1)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:554)
    at org.eclipse.osgi.internal.framework.BundleContextImpl.startActivator(BundleContextImpl.java:806)
    ... 27 more
Root exception:
org.eclipse.core.internal.dtree.ObjectNotFoundException: Tree element '/04-HA-Advanced-StopWatch-Muster/src/idh/java/ha/StopWatch.java' not found.
    at org.eclipse.core.internal.dtree.AbstractDataTree.handleNotFound(AbstractDataTree.java:260)
    at org.eclipse.core.internal.dtree.DeltaDataTree.getData(DeltaDataTree.java:599)
    at org.eclipse.core.internal.dtree.DataDeltaNode.asBackwardDelta(DataDeltaNode.java:54)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.DataDeltaNode.asBackwardDelta(DataDeltaNode.java:51)
    at org.eclipse.core.internal.dtree.DeltaDataTree.asBackwardDelta(DeltaDataTree.java:91)
    at org.eclipse.core.internal.dtree.DeltaDataTree.reroot(DeltaDataTree.java:835)
    at org.eclipse.core.internal.dtree.DeltaDataTree.reroot(DeltaDataTree.java:834)
    at org.eclipse.core.internal.dtree.DeltaDataTree.reroot(DeltaDataTree.java:811)
    at org.eclipse.core.internal.watson.ElementTree.immutable(ElementTree.java:522)
    at org.eclipse.core.internal.resources.SaveManager.restore(SaveManager.java:731)
    at org.eclipse.core.internal.resources.SaveManager.startup(SaveManager.java:1555)
    at org.eclipse.core.internal.resources.Workspace.startup(Workspace.java:2452)
    at org.eclipse.core.internal.resources.Workspace.open(Workspace.java:2210)
    at org.eclipse.core.resources.ResourcesPlugin.start(ResourcesPlugin.java:489)
    at org.eclipse.osgi.internal.framework.BundleContextImpl$2.run(BundleContextImpl.java:814)
    at org.eclipse.osgi.internal.framework.BundleContextImpl$2.run(BundleContextImpl.java:1)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:554)
    at org.eclipse.osgi.internal.framework.BundleContextImpl.startActivator(BundleContextImpl.java:806)
    at org.eclipse.osgi.internal.framework.BundleContextImpl.start(BundleContextImpl.java:763)
    at org.eclipse.osgi.internal.framework.EquinoxBundle.startWorker0(EquinoxBundle.java:1011)
    at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.startWorker(EquinoxBundle.java:365)
    at org.eclipse.osgi.container.Module.doStart(Module.java:605)
    at org.eclipse.osgi.container.Module.start(Module.java:468)
    at org.eclipse.osgi.framework.util.SecureAction.start(SecureAction.java:506)
    at org.eclipse.osgi.internal.hooks.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:117)
    at org.eclipse.osgi.internal.loader.classpath.ClasspathManager.findLocalClass(ClasspathManager.java:572)
    at org.eclipse.osgi.internal.loader.ModuleClassLoader.findLocalClass(ModuleClassLoader.java:346)
    at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:398)
    at org.eclipse.osgi.internal.loader.sources.SingleSourcePackage.loadClass(SingleSourcePackage.java:41)
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:473)
    at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:171)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:151)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:657)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:594)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1465)

!ENTRY org.eclipse.osgi 4 0 2020-11-26 10:13:44.910
!MESSAGE Application error
!STACK 1
java.lang.NoClassDefFoundError: org/eclipse/core/resources/IContainer
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:151)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:401)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:657)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:594)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1465)
Caused by: java.lang.ClassNotFoundException: An error occurred while automatically activating bundle org.eclipse.core.resources (591).
    at org.eclipse.osgi.internal.hooks.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:126)
    at org.eclipse.osgi.internal.loader.classpath.ClasspathManager.findLocalClass(ClasspathManager.java:572)
    at org.eclipse.osgi.internal.loader.ModuleClassLoader.findLocalClass(ModuleClassLoader.java:346)
    at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:398)
    at org.eclipse.osgi.internal.loader.sources.SingleSourcePackage.loadClass(SingleSourcePackage.java:41)
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:473)
    at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:171)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
    ... 13 more
Caused by: org.osgi.framework.BundleException: Exception in org.eclipse.core.resources.ResourcesPlugin.start() of bundle org.eclipse.core.resources.
    at org.eclipse.osgi.internal.framework.BundleContextImpl.startActivator(BundleContextImpl.java:835)
    at org.eclipse.osgi.internal.framework.BundleContextImpl.start(BundleContextImpl.java:763)
    at org.eclipse.osgi.internal.framework.EquinoxBundle.startWorker0(EquinoxBundle.java:1011)
    at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.startWorker(EquinoxBundle.java:365)
    at org.eclipse.osgi.container.Module.doStart(Module.java:605)
    at org.eclipse.osgi.container.Module.start(Module.java:468)
    at org.eclipse.osgi.framework.util.SecureAction.start(SecureAction.java:506)
    at org.eclipse.osgi.internal.hooks.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:117)
    ... 20 more
Caused by: org.eclipse.core.internal.dtree.ObjectNotFoundException: Tree element '/04-HA-Advanced-StopWatch-Muster/src/idh/java/ha/StopWatch.java' not found.
    at org.eclipse.core.internal.dtree.AbstractDataTree.handleNotFound(AbstractDataTree.java:260)
    at org.eclipse.core.internal.dtree.DeltaDataTree.getData(DeltaDataTree.java:599)
    at org.eclipse.core.internal.dtree.DataDeltaNode.asBackwardDelta(DataDeltaNode.java:54)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.NoDataDeltaNode.asBackwardDelta(NoDataDeltaNode.java:63)
    at org.eclipse.core.internal.dtree.DataDeltaNode.asBackwardDelta(DataDeltaNode.java:51)
    at org.eclipse.core.internal.dtree.DeltaDataTree.asBackwardDelta(DeltaDataTree.java:91)
    at org.eclipse.core.internal.dtree.DeltaDataTree.reroot(DeltaDataTree.java:835)
    at org.eclipse.core.internal.dtree.DeltaDataTree.reroot(DeltaDataTree.java:834)
    at org.eclipse.core.internal.dtree.DeltaDataTree.reroot(DeltaDataTree.java:811)
    at org.eclipse.core.internal.watson.ElementTree.immutable(ElementTree.java:522)
    at org.eclipse.core.internal.resources.SaveManager.restore(SaveManager.java:731)
    at org.eclipse.core.internal.resources.SaveManager.startup(SaveManager.java:1555)
    at org.eclipse.core.internal.resources.Workspace.startup(Workspace.java:2452)
    at org.eclipse.core.internal.resources.Workspace.open(Workspace.java:2210)
    at org.eclipse.core.resources.ResourcesPlugin.start(ResourcesPlugin.java:489)
    at org.eclipse.osgi.internal.framework.BundleContextImpl$2.run(BundleContextImpl.java:814)
    at org.eclipse.osgi.internal.framework.BundleContextImpl$2.run(BundleContextImpl.java:1)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:554)
    at org.eclipse.osgi.internal.framework.BundleContextImpl.startActivator(BundleContextImpl.java:806)
    ... 27 more

This seemed to have caused the Problem:
!MESSAGE The workspace exited with unsaved changes in the previous session; refreshing workspace to recover changes.

I solved the Problem by deleting (and backupping) .snap and .tree files.:
this
and this

That resulted in the next problem I'm having right now. I tried solving the problem by reimporting my projects as "Smug" advised in this post here:

Btw. I organize my projects into java working sets. Don't know if that makes any difference.

Ichigo Kurosaki
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Joshua Krueger
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    If you have backed up the entire `.metadata` folder restore it and follow the documentation by starting Eclipse with the `-clean` option rather than following Stack Overflow answers proposing to delete random files that are not intended to be deleted manually. If `-clean` does not help, switch to a fresh workspace and import your projects from the old workspace. – howlger Nov 26 '20 at 12:52
  • Do you mean a Backup before the problems started? Then I don't have one. I only have the files I deleted manually. – Joshua Krueger Nov 26 '20 at 22:00
  • Yes, before the problems started. You might try `-clean` anyway. Did you tell those who suggested deleting random files that it did not work and causing damage? – howlger Nov 27 '20 at 09:00
  • I can't reply to the posts as I'm a newbie and do not have enough reputation... I'll check out -clean and try it out. – Joshua Krueger Nov 27 '20 at 20:18

1 Answers1

0

Solved the problem by following the advice of those two:

Jay: "so I am a little late for the party, but I fixed that on reimporting my projects.

Under File->Import.. you choose General->Import existing Projects into workspace. On the next page you set your workspace directory as the root directory for importing, which will give you a warning like "Some projects already exist in workspace". Ignore this and click finish. After that all my projects where back in my workspace.

Good luck" Eclipse Error: Cannot determine URI for /project-path/

and

Rekinyz: "Uncheck the "copy projects into workspace" checkbox, and then click "refresh" button, you will be able to import the project". Some projects cannot be imported because they already exist in the workspace error in Eclipse

If you use working sets, remember to reimport all the projects in the right ones...

Joshua Krueger
  • 1