使用Eclipse查看.class文件时，显示The class file is not on the classpath。
请问有什么方法可以解决？
Details：
org.eclipse.core.runtime.CoreException: The class file is not on the classpath
at org.eclipse.jdt.internal.ui.javaeditor.ClassFileEditor.doSetInput(ClassFileEditor.java:670)
at org.eclipse.ui.texteditor.AbstractTextEditor.lambda$1(AbstractTextEditor.java:3168)
at org.eclipse.jface.operation.ModalContext.runInCurrentThread(ModalContext.java:434)
at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:352)
at org.eclipse.ui.internal.WorkbenchWindow.lambda$7(WorkbenchWindow.java:2345)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:74)
at org.eclipse.ui.internal.WorkbenchWindow.run(WorkbenchWindow.java:2343)
at org.eclipse.ui.texteditor.AbstractTextEditor.internalInit(AbstractTextEditor.java:3185)
at org.eclipse.ui.texteditor.AbstractTextEditor.init(AbstractTextEditor.java:3210)
at org.eclipse.ui.internal.EditorReference.initialize(EditorReference.java:353)
at org.eclipse.ui.internal.e4.compatibility.CompatibilityPart.create(CompatibilityPart.java:344)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:58)
at org.eclipse.e4.core.internal.di.InjectorImpl.processAnnotated(InjectorImpl.java:995)
at org.eclipse.e4.core.internal.di.InjectorImpl.processAnnotated(InjectorImpl.java:960)
at org.eclipse.e4.core.internal.di.InjectorImpl.internalInject(InjectorImpl.java:140)
at org.eclipse.e4.core.internal.di.InjectorImpl.internalMake(InjectorImpl.java:403)
at org.eclipse.e4.core.internal.di.InjectorImpl.make(InjectorImpl.java:330)
at org.eclipse.e4.core.contexts.ContextInjectionFactory.make(ContextInjectionFactory.java:202)
at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.createFromBundle(ReflectionContributionFactory.java:91)
at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.doCreate(ReflectionContributionFactory.java:60)
at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.create(ReflectionContributionFactory.java:42)
at org.eclipse.e4.ui.workbench.renderers.swt.ContributedPartRenderer.createWidget(ContributedPartRenderer.java:132)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createWidget(PartRenderingEngine.java:994)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:658)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:762)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$2.run(PartRenderingEngine.java:727)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:45)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:711)
at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.lambda$0(PartServiceImpl.java:105)
at org.eclipse.e4.ui.services.internal.events.UIEventHandler.lambda$0(UIEventHandler.java:38)
at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:236)
at org.eclipse.ui.internal.UISynchronizer.syncExec(UISynchronizer.java:133)
at org.eclipse.swt.widgets.Display.syncExec(Display.java:4779)
at org.eclipse.e4.ui.workbench.swt.DisplayUISynchronize.syncExec(DisplayUISynchronize.java:34)
at org.eclipse.e4.ui.services.internal.events.UIEventHandler.handleEvent(UIEventHandler.java:38)
at org.eclipse.equinox.internal.event.EventHandlerWrapper.handleEvent(EventHandlerWrapper.java:205)
at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:203)
at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:1)
at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:228)
at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:151)
at org.eclipse.equinox.internal.event.EventAdminImpl.dispatchEvent(EventAdminImpl.java:133)
at org.eclipse.equinox.internal.event.EventAdminImpl.sendEvent(EventAdminImpl.java:75)
at org.eclipse.equinox.internal.event.EventComponent.sendEvent(EventComponent.java:44)
at org.eclipse.e4.ui.services.internal.events.EventBroker.send(EventBroker.java:55)
at org.eclipse.e4.ui.internal.workbench.UIEventPublisher.notifyChanged(UIEventPublisher.java:63)
at org.eclipse.emf.common.notify.impl.BasicNotifierImpl.eNotify(BasicNotifierImpl.java:424)
at org.eclipse.e4.ui.model.application.ui.impl.ElementContainerImpl.setSelectedElementGen(ElementContainerImpl.java:170)
at org.eclipse.e4.ui.model.application.ui.impl.ElementContainerImpl.setSelectedElement(ElementContainerImpl.java:188)
at org.eclipse.e4.ui.internal.workbench.ModelServiceImpl.showElementInWindow(ModelServiceImpl.java:660)
at org.eclipse.e4.ui.internal.workbench.ModelServiceImpl.bringToTop(ModelServiceImpl.java:624)
at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.delegateBringToTop(PartServiceImpl.java:787)
at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.showPart(PartServiceImpl.java:1258)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditor(WorkbenchPage.java:3208)
at org.eclipse.ui.internal.WorkbenchPage.lambda$9(WorkbenchPage.java:3112)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:74)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:3110)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:3080)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:3063)
at org.eclipse.ui.internal.ReopenEditorMenu.open(ReopenEditorMenu.java:282)
at org.eclipse.ui.internal.ReopenEditorMenu$1.lambda$0(ReopenEditorMenu.java:232)
at org.eclipse.swt.events.SelectionListener$1.widgetSelected(SelectionListener.java:84)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:252)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4243)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1060)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4060)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3632)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1154)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1045)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:155)
at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:644)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:551)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:156)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:152)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:136)
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:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:659)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:596)
at org.eclipse.equinox.launcher.Main.run(Main.java:1467)
