JavaEditor editor = (JavaEditor)EditorUtility.openInEditor(unit);
JavaSourceViewer viewer = (JavaSourceViewer)editor.getViewer();
JavaContentAssistInvocationContext context =
new JavaContentAssistInvocationContext(viewer, offset, editor);
IJavaCompletionProposalComputer computer =
new GroovyCompletionProposalComputer();
List<ICompletionProposal> proposals =
computer.computeCompletionProposals(context, null);
editor.close(false);
if(proposals == null){
proposals = Collections.emptyList();