private static CommonTree runParser(CharStream charStream) throws Exception { FilterLexer lex = new FilterLexer(charStream); CommonTokenStream tokens = new CommonTokenStream(lex); FilterParser g = new FilterParser(tokens); try { filter_return fr = g.filter(); CommonTree tree = (CommonTree) fr.getTree(); return tree; } catch (RecognitionException e) { e.printStackTrace(); return null; } }