The printf Method

The printf method is another way to format output. It

is based on the printf function of the C language.

System.out.printf(<format string>, <arg1>,

<arg2>, ..., <argn>);

The format string is a string that specifies how to

print out the output, and the args specify the values

that are to be printed out.

Example

String name = "Foobear";int n = 10;double f = -132.5;System.out.printf("%s %5d %6.2f", name, n, f);

will print out:

Foobear 10 -132.50

with no end of line at the end.

Format Specifiers

The format string contains format specifiers. There is

a format specifier corresponding to each argument.

The first format specifier is used for the first

argument, the second for the second argument, and

so on. The format specifier specifies the how the

argument is to be interpreted (decimal, fixed-point,

exponential notation, string, character), and,

optionally, the field width, the precision, and the

justification.

Specifier Form

The general form of a format specifier is:

%-w.pc

where – means to left justify, w is the field width, p

is the precision, and c is the conversion character.

Everything is optional except for the '%' and c.

Thus, a format specifier could be just

%c

Conversion Characters

The most commonly used conversion characters are: d – decimal (ordinary) integer f – fixed point floating point number e – exponential (scientific notation) floating point g – general floating point (Java decides between

the previous two) s – string c - character

Optional Specifications

The optional parts of the format specifier are: - left justify. Without this, the value is right

justified. w – (an integer) field width. If the value printed

out takes fewer than w columns, it is padded with

spaces. p – (an integer) precision. The number of digits to

the right of the decimal point.

Added Text

The format string may also contain text, which is

printed out as is. This is used for labels, for $ (for

money), spacing, and new lines. The code %n will

output a new line character.

System.out.printf("You are owed $%6.2f. %n", money);