INTRODUCTION TO OBJECTS AND INPUT/OUTPUT - Java Programming: From Problem Analysis to Program Design - page 131

It follows that when outputting the format string, the format specifiers are replaced with
the formatted values of the corresponding arguments.
A format specifier for general, character, and numeric types has the following syntax:

%[argument_index$][flags][width][.precision]conversion

3

The expressions in square brackets are optional. That is, they may or may not appear in a
format specifier.
The option argument_index is a (decimal) integer indicating the position of the
argument in the argument list. The first argument is referenced by "1$" ,thesecond
by "2$" , and so on.
The option flags is a set of characters that modifies the output format. The set of valid flags
depends on the conversion.
The option width is a (decimal) integer indicating the minimum number of characters to
be written to the output.
The option precision is a (decimal) integer usually used to restrict the number of characters.
The specific behavior depends on the conversion.
The required conversion is a character indicating how the argument should be formatted.
The set of valid conversions for a given argument depends on the argument's data type.
Table 3-2 summarizes some of the supported conversions.

TABLE 3-2 Some of Java's Supported Conversions

's'

general The result is a string

'c' character The result is a Unicode character

'd' integral The result is formatted as a (decimal) integer

The result is formatted as a decimal number in
computerized scientific notation

'e'

floating point

'f'

floating point The result is formatted as a decimal number

'%' The result is '%'

percent

'n' line separator The result is the platform-specific line separator

The method printf is available in Java 5.0 and higher versions.
The following example shows how the conversions f and e work to output floating-
point numbers in fixed decimal and scientific formats.