簡単な例：0以上の繰り返し

PARSER_BEGIN(Test)

public class Test {
  public static void main(String args[]) throws ParseException {
    Test parser = new Test(System.in);
    parser.Input();
  }
}

PARSER_END(Test)

SKIP :
{
    <SPACE:  " " | "\t" | "\n" | "\r">
}

void Input() :
{}
{
    ( "a" )* <EOF>
}

で、

a
aa
aaa

b
Exception in thread "main" TokenMgrError: Lexical error at line 5, column 1.  Encountered: "b" (98), after : ""
	at TestTokenManager.getNextToken(TestTokenManager.java:268)
	at Test.jj_ntk(Test.java:145)
	at Test.Input(Test.java:11)
	at Test.main(Test.java:5)