<interfaces> ::= <interface> {<interface>}
<interface> ::= interface <name> [<extends>] ('{' [<methods>] [<interfaces>] '}')

<extends> ::= extends <name> {(',') <name>}

<type> ::= (<int> | <void> | <String> | <boolean>)

<declaration> ::= <type> <name>

<methods> ::= <method> { <method> }

<method> ::= <declaration> '(' [ <parameters> ] ')' ';'

<paramameters> ::= <declaration> { (',') <declaration> }