Error when opening Eclipse

Could not open the editor: The editor class could not be instantiated. This usually indicates a missing no-arg constructor or that the editor's class name was mistyped in plugin.xml.

Trace

org.eclipse.core.runtime.internal.adaptor.EclipseLazyStarter$TerminatingClassNotFoundException: An error occurred while automatically activating bundle org.eclipse.jdt.ui (311).
	at org.eclipse.core.runtime.internal.adaptor.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:125)
	at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClass(ClasspathManager.java:449)
	at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.findLocalClass(DefaultClassLoader.java:211)
	at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:381)
	at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:457)
	at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:410)
	at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:398)
	at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:105)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
	at org.eclipse.osgi.internal.loader.BundleLoader.loadClass(BundleLoader.java:326)
	at org.eclipse.osgi.framework.internal.core.BundleHost.loadClass(BundleHost.java:231)
	at org.eclipse.osgi.framework.internal.core.AbstractBundle.loadClass(AbstractBundle.java:1193)
	at org.eclipse.core.internal.registry.osgi.RegistryStrategyOSGI.createExecutableExtension(RegistryStrategyOSGI.java:160)
	at org.eclipse.core.internal.registry.ExtensionRegistry.createExecutableExtension(ExtensionRegistry.java:874)
	at org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(ConfigurationElement.java:243)
	at org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(ConfigurationElementHandle.java:51)
	at org.eclipse.ui.internal.WorkbenchPlugin$1.run(WorkbenchPlugin.java:267)
	at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
	at org.eclipse.ui.internal.WorkbenchPlugin.createExtension(WorkbenchPlugin.java:263)
	at org.eclipse.ui.internal.registry.EditorDescriptor.createEditor(EditorDescriptor.java:235)
	at org.eclipse.ui.internal.EditorManager.createPart(EditorManager.java:845)
	at org.eclipse.ui.internal.EditorReference.createPartHelper(EditorReference.java:606)
	at org.eclipse.ui.internal.EditorReference.createPart(EditorReference.java:462)
	at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:595)
	at org.eclipse.ui.internal.EditorAreaHelper.setVisibleEditor(EditorAreaHelper.java:271)
	at org.eclipse.ui.internal.EditorManager.setVisibleEditor(EditorManager.java:1417)
	at org.eclipse.ui.internal.EditorManager$5.runWithException(EditorManager.java:942)
	at org.eclipse.ui.internal.StartupThreading$StartupRunnable.run(StartupThreading.java:31)
	at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
	at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:134)
	at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:3342)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3071)
	at org.eclipse.ui.application.WorkbenchAdvisor.openWindows(WorkbenchAdvisor.java:803)
	at org.eclipse.ui.internal.Workbench$28.runWithException(Workbench.java:1384)
	at org.eclipse.ui.internal.StartupThreading$StartupRunnable.run(StartupThreading.java:31)
	at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
	at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:134)
	at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:3342)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3071)
	at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2316)
	at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2221)
	at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:500)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:493)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:194)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:368)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:592)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:559)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1311)
Caused by: org.osgi.framework.BundleException: The activator org.eclipse.jdt.internal.ui.JavaPlugin for bundle org.eclipse.jdt.ui is invalid
	at org.eclipse.osgi.framework.internal.core.AbstractBundle.loadBundleActivator(AbstractBundle.java:157)
	at org.eclipse.osgi.framework.internal.core.BundleContextImpl.start(BundleContextImpl.java:751)
	at org.eclipse.osgi.framework.internal.core.BundleHost.startWorker(BundleHost.java:352)
	at org.eclipse.osgi.framework.internal.core.AbstractBundle.start(AbstractBundle.java:280)
	at org.eclipse.osgi.framework.util.SecureAction.start(SecureAction.java:408)
	at org.eclipse.core.runtime.internal.adaptor.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:111)
	... 57 more
Caused by: java.lang.NoClassDefFoundError: org/eclipse/jdt/core/IBufferFactory
	at java.lang.Class.getDeclaredConstructors0(Native Method)
	at java.lang.Class.privateGetDeclaredConstructors(Class.java:2357)
	at java.lang.Class.getConstructor0(Class.java:2671)
	at java.lang.Class.newInstance0(Class.java:321)
	at java.lang.Class.newInstance(Class.java:303)
	at org.eclipse.osgi.framework.internal.core.AbstractBundle.loadBundleActivator(AbstractBundle.java:152)
	... 62 more