[antlr-interest] 'backtrack' not expected ';'

[yu xiang]

In my grammer I wrote like this

************************
options {
 language=Java;
 k=*;
 backtrack=true;
 memoize=true;
 output=AST;
}
************************

When I generate the code, there is always the error 'backtrack' not expected
';'
I don't kown what's wrong with it.
Can anyone give me some help, thankyou!