Java The Complete Reference, Seventh Edition

526 Part II: The Java Library

The Formatter Constructors

Before you can useFormatterto format output, you must create aFormatterobject. In general,

Formatterworks by converting the binary form of data used by a program into formatted

text. It stores the formatted text in a buffer, the contents of which can be obtained by your

program whenever they are needed. It is possible to letFormattersupply this buffer

automatically, or you can specify the buffer explicitly when aFormatterobject is created.

It is also possible to haveFormatteroutput its buffer to a file.

TheFormatterclass defines many constructors, which enable you to construct aFormatter

in a variety of ways. Here is a sampling:

Formatter( )

Formatter(Appendablebuf)

Formatter(Appendablebuf, Localeloc)

Formatter(Stringfilename)

throws FileNotFoundException

Formatter(Stringfilename, Stringcharset)

throws FileNotFoundException, UnsupportedEncodingException

Formatter(FileoutF)

throws FileNotFoundException

Formatter(OutputStreamoutStrm)

Here,bufspecifies a buffer for the formatted output. Ifbufis null, thenFormatterautomatically

allocates aStringBuilderto hold the formatted output. Thelocparameter specifies a locale.

If no locale is specified, the default locale is used. Thefilenameparameter specifies the name

of a file that will receive the formatted output. Thecharsetparameter specifies the character

set. If no character set is specified, then the default character set is used. TheoutFparameter

specifies a reference to an open file that will receive output. TheoutStrmparameter specifies

a reference to an output stream that will receive output. When using a file, output is also

written to the file.

Perhaps the most widely used constructor is the first, which has no parameters.

It automatically uses the default locale and allocates aStringBuilderto hold the formatted

output.

The Formatter Methods

Formatterdefines the methods shown in Table 18-11.

Formatting Basics

After you have created aFormatter, you can use it to create a formatted string. To do so, use

theformat( )method. The most commonly used version is shown here:

Formatter format(StringfmtString, Object ...args)