Formatter provides the method to give out formatted string just like the printf-style. Layout,alignment and other format flags are provided to format numeric,string and date/time as well as locale-specified formats applied. Besides primitive types, formatter also support some java object types such as BigInteger,BigDecimal and Calendar. Customized formatting is provided through the Formattable interface. The class is not multi-threaded safe. The responsibility to maintain thread safety is the user's job.