Input and Output - Java - page 369

Table 10-1. Formatter format codes

Code Meaning

c Character (argument must be char or integral type containing valid character value).

d “decimal int”—integer to be printed as a decimal (radix 10) with no decimal point (argument must

be integral type).

f Floating-point value with decimal fraction (must be numeric); field width may be followed by

decimal point and fractional digit field width; e.g., 7.2f.

e Floating-point value in scientific notation.

g Floating-point value, as per f or e, depending on magnitude.

s General format; if value is null, prints “null,” else if arg implements Formattable , format as per

arg.formatTo() ; else format as per arg.toString() .

t Date codes; follow with secondary code. Common date codes are shown in Table 10-2 . Argument

must be long , Long , Calendar , or Date .

n Newline; insert the platform-dependent line ending character.

% Insert a literal % character.

Note also that you may, but are not required to, put a “parameter order” number between the
% and the format code. For example, in “%2$04d”, the “2$” means to format the second para-
meter, regardless of the order of the parameters. This is primarily useful with dates (see the
following example, where you need to format several different portions of the same Date or
Calendar , or any time you want to format the same object more than once) and in interna-
tionalization, where different languages may require words to be in a different order within a
sentence.

Some examples of using a Formatter are shown in Example 10-2 .

Example 10-2. src/main/java/io/FormatterDemo.java
public public class class FormatterDemo FormatterDemo {

public public static static void void main ( String [] args ) {

// The arguments to all these format methods consist of
// a format code String and 1 or more arguments.