If you are executing code in the current Non-UI thread, then you can ask the Display to render a model dialog box with the following code:

 * Show an information dialog box.
public void showInformation(final String title, final String message) {
  Display.getDefault().asyncExec(new Runnable() {
    public void run() {
      MessageDialog.openInformation(null, title, message);

ErrorDialog the error message-displaying equivalent of MessageDialog.

IF you were in a UI thread, you could achieve a dialog box with just this:

boolean result = MessageDialog.openConfirm(PlatformUI
    .getShell(), title, message);