[antlr-interest] question on java.g 1.6

[Jeremy Long]

I am still fairly new to antlr and when looking at the 1.6 Java grammar I
noticed the following statement rule:

statement
    :   block

    |   ('assert'
        )
        expression (':' expression)? ';'
    |   'assert'  expression (':' expression)? ';'
    |   'if' parExpression statement ('else' statement)?
    |   forstatement
    |   'while' parExpression statement
    |   'do' statement 'while' parExpression ';'
    |   trystatement
    |   'switch' parExpression '{' switchBlockStatementGroups '}'
    |   'synchronized' parExpression block
    |   'return' (expression )? ';'
    |   'throw' expression ';'
    |   'break'
            (IDENTIFIER
            )? ';'
    |   'continue'
            (IDENTIFIER
            )? ';'
    |   expression  ';'
    |   IDENTIFIER ':' statement
    |   ';'
    ;


My question is about the two lines for assert:
    |   ('assert'
        )
        expression (':' expression)? ';'
    |   'assert'  expression (':' expression)? ';'
To me those look identicle - am I missing something? Is there some nuance
to the parens that I don't understand?

Thanks,

jeremy