if (ast == null) return null;
	public IRegion getHoverRegion(ITextViewer textViewer, int offset) {		if (!(getEditor() instanceof JavaEditor))			return null;		IJavaElement je= getEditorInputJavaElement();		if (je == null)			return null;				// Never wait for an AST in UI thread.		CompilationUnit ast= JavaPlugin.getDefault().getASTProvider().getAST(je, ASTProvider.WAIT_NO, null);		ASTNode node= NodeFinder.perform(ast, offset, 1);		if (!(node instanceof StringLiteral))			return null;		StringLiteral stringLiteral= (StringLiteral)node;				return new Region(stringLiteral.getStartPosition(), stringLiteral.getLength());	}