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;
}
}
