Create some projects/resources ...delete them and you get about a zillion of these:

java.lang.NullPointerException
at org.jboss.ide.eclipse.archives.core.WorkspaceChangeListener$1.visit(WorkspaceChangeListener.java:57)
at org.eclipse.core.internal.events.ResourceDelta.accept(ResourceDelta.java:67)
at org.eclipse.core.internal.events.ResourceDelta.accept(ResourceDelta.java:76)
at org.eclipse.core.internal.events.ResourceDelta.accept(ResourceDelta.java:48)
at org.jboss.ide.eclipse.archives.core.WorkspaceChangeListener.resourceChanged(WorkspaceChangeListener.java:55)
at org.eclipse.core.internal.events.NotificationManager$2.run(NotificationManager.java:282)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:37)
at org.eclipse.core.internal.events.NotificationManager.notify(NotificationManager.java:276)
at org.eclipse.core.internal.events.NotificationManager.broadcastChanges(NotificationManager.java:148)
at org.eclipse.core.internal.resources.Workspace.broadcastPostChange(Workspace.java:311)
at org.eclipse.core.internal.resources.Workspace.endOperation(Workspace.java:1018)
at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:1806)
at org.eclipse.ui.ide.undo.AbstractWorkspaceOperation.execute(AbstractWorkspaceOperation.java:204)
at org.eclipse.ui.actions.DeleteResourceAction$4.run(DeleteResourceAction.java:533)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)