Numbers will be converted to Double. The grammar is given here . An I w element accepts an Integer or Long, and outputs it in a field of width w . Positive or zero numbers are output with no sign and no leading zeroes. Negative numbers have a sign.
All integers are right-justified with spaces.
The structure is simple in essence, but complicated by the need to pass information around for extensive error-checking. A Formatter contains an instance of class Format , which represents a complete format. Some of these are FormatIOElements , meaning that they transfer data. These are further subclassed as FormatI , FormatF and so on. All these format classes have read and write methods.