antlr: how to use String.format inside action

Question

I have the a rule with an action defined as follows:

metric_expr
  : metric=NAME ('AS' label=NAME)? {System.out.println(String.format("%s: %s", metric, label));}
  ;

I got the error says:

error(146): com\foo\bar\PRL.g:65:54: invalid StringTemplate % shorthand syntax: '%s'

Anyone know how to workaround this?

Answer 1

Escape the % signs with a single backslash.

And if you want to display the text of a token, use the token's .text attribute:

metric_expr
  : metric=NAME ('AS' label=NAME)? 
    {System.out.printf("\%s: \%s", $metric.text, $label.text);}
  ;