anchor.diff:      :    Identifier | Identifier '<' JavaClassType '>'
       ;
   
  -
   /**
    * Literals, a much more simple version than Java literals.
    * For numeric literals, only support decimal.
  
positive.code:     ;
  DoubleLiteral
      :    [+-]? ([1-9]+ 0*)* [0-9] '.' [0-9]+ 'd'
      ;
  
  /**
  
negative.code:     | DoubleLiteral
      ;
  StringLiteral //? support unicode should check
      :    '"' (()+)? '"'
      ;    
  CharLiteral
      :    '\'' SingleCharacter '\''
      |    '\'' EscapeSequence '\''
      ;
  BooleanLiteral
      :    TRUE | FALSE
  