[java] NullPointerException in eclipse in Eclipse itself at PartServiceImpl.internalFixContext

I have a problem about eclipse IDE, I can't open any file in my work space; if I try to open file, eclipse will alert the following error dialog

"An error has occurred. See error log for more details. java.lang.NullPointerException"

I go to see .log file in .meta at workspace and I see a paragraph in the file like this:

!ENTRY org.eclipse.jface 4 2 2557-04-09 11:40:49.422
!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.jface".
!STACK 0
java.lang.NullPointerException
    at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.internalFixContext(PartServiceImpl.java:380)
    at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.bringToTop(PartServiceImpl.java:341)
    at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.showPart(PartServiceImpl.java:1029)
    at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditor(WorkbenchPage.java:3047)
    at org.eclipse.ui.internal.WorkbenchPage.access$22(WorkbenchPage.java:2969)
    at org.eclipse.ui.internal.WorkbenchPage$8.run(WorkbenchPage.java:2951)
    at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
    at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2947)
    at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2911)
    at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2902)
    at org.eclipse.ui.ide.IDE.openEditor(IDE.java:655)
    at org.eclipse.ui.ide.IDE.openEditor(IDE.java:614)
    at org.eclipse.jdt.internal.ui.javaeditor.EditorUtility.openInEditor(EditorUtility.java:360)
    at org.eclipse.jdt.internal.ui.javaeditor.EditorUtility.openInEditor(EditorUtility.java:167)
    at org.eclipse.jdt.ui.actions.OpenAction.run(OpenAction.java:249)
    at org.eclipse.jdt.ui.actions.OpenAction.run(OpenAction.java:228)
    at org.eclipse.jdt.ui.actions.SelectionDispatchAction.dispatchRun(SelectionDispatchAction.java:275)
    at org.eclipse.jdt.ui.actions.SelectionDispatchAction.run(SelectionDispatchAction.java:251)
    at org.eclipse.jdt.internal.ui.packageview.PackageExplorerActionGroup.handleOpen(PackageExplorerActionGroup.java:376)
    at org.eclipse.jdt.internal.ui.packageview.PackageExplorerPart$4.open(PackageExplorerPart.java:538)
    at org.eclipse.ui.OpenAndLinkWithEditorHelper$InternalListener.open(OpenAndLinkWithEditorHelper.java:48)
    at org.eclipse.jface.viewers.StructuredViewer$2.run(StructuredViewer.java:866)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:49)
    at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
    at org.eclipse.jface.viewers.StructuredViewer.fireOpen(StructuredViewer.java:864)
    at org.eclipse.jface.viewers.StructuredViewer.handleOpen(StructuredViewer.java:1152)
    at org.eclipse.jface.viewers.StructuredViewer$6.handleOpen(StructuredViewer.java:1256)
    at org.eclipse.jface.util.OpenStrategy.fireOpenEvent(OpenStrategy.java:275)
    at org.eclipse.jface.util.OpenStrategy.access$2(OpenStrategy.java:269)
    at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:309)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4169)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3758)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1053)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:942)
    at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:86)
    at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:588)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:543)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
    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:353)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
    at org.eclipse.equinox.launcher.Main.main(Main.java:1414)

How can I solve this problem - any idea?

I faced the same error, but only with files cloned from git that were assigned to a proprietary plugin. I realized that even after cloning the files from git, I needed to create a new project or import a project in eclipse and this resolved the error.

hi,that maybe the project's problem,

chose the project and setting you eclipse:

project -> clean... 

After exiting eclipse I moved .eclipse (found in the user's home directory) to .eclipse.old (just in case I may have had to undo). The error does not show up any more and my projects are working fine after restarting eclipse.

Caution: I have a simple setup and this may not be the best for environments with advanced settings.

I am posting this as a separate answer as previously listed methods did not work for me.

I have also encountered this error . Just i opened the new window ie Window -> New Window in eclipse .Then , I closed my old window. This solved my problem.

Better you update your eclipse by clicking it on help >> check for updates, also you can start eclipse by entering command in command prompt eclipse -clean.
Hope this will help you.