public void importTokensFromTokensFile() {
String vocab = getOptionString("tokenVocab");
if ( vocab!=null ) {
TokenVocabParser vparser = new TokenVocabParser(this);
Map<String,Integer> tokens = vparser.load();
tool.log("grammar", "tokens=" + tokens);
for (String t : tokens.keySet()) {
if ( t.charAt(0)=='\'' ) defineStringLiteral(t, tokens.get(t));
else defineTokenName(t, tokens.get(t));
}