Bug 19075 Rename Java file to non Java file causes most actions to crash
F2 - open Java file in editor - rename it so that it has the extension .txt Almost all Java relevant actions in Edit, Source, Refactor, Naviagte and context menu are still enabled. Executing them almost always leads to some sort of exceptions.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitEditor.java
protected ISelectionChangedListener fStatusLineClearer;
	
	protected ISavePolicy fSavePolicy;
	
	private JavaEditorErrorTickUpdater fJavaEditorErrorTickUpdater;
	
	private PaintManager fPaintManager;
	
	private BracketPainter fBracketPainter;
	
	private LinePainter fLinePainter;
	
	private PrintMarginPainter fPrintMarginPainter;
	
	private ProblemPainter fProblemPainter;
	
	private TabConverter fTabConverter;
	
	private SelectionHistory fSelectionHistory;
	
	private IPropertyChangeListener fPropertyChangeListener= new PropertyChangeListener();
	
	private IJavaElement fRememberedElement;
	
	private ITextSelection fRememberedSelection;
	
	private int fRememberedElementOffset;