Java Reference
In-Depth Information
tained from its out method (see Section 22.1.8 on page 631 ).
The flags , width , and precision arguments contain the flags,
width, and precision values that were used in the string con-
version format specifier. If no width or precision was given,
then 1 is passed. The flags are encoded as a bit mask from
the constants of the FormattableFlags class. Only two flags are
supported: LEFT_JUSTIFY , which indicates the flag for left-jus-
tification, and ALTERNATE , which indicates the # flag. Each For-
mattable class is free to define what ALTERNATE means.
Additionally, the flag value encodes whether the conversion indicator
was lowercase or uppercase using the FormattableFlags.UPPERCASE con-
stant. You can test whether a flag is set by AND ing the flags value with
the desired constant and seeing if the result is non-zero.
By implementing Formattable a class can provide greater flexibility in
how it represents itself textually, compared to the fixed output of the
toString method. For example, it can use a long or short form, depend-
ing on the width and precision that were supplied; or it can adapt itself
to the locale used by the formattersee page 632 .
22.1.7. Format Exceptions
If any errors occur while processing a format string with a given set of
arguments, an exception that is a subclass of IllegalFormatException will
be thrown. The types of exception you can encounter are
DuplicateFormatFlagsException A flag was used more than once.
FormatFlagsConversionMismatchException A flag was incompatible
with the conversion.
IllegalFormatCodePointException An integer value was passed that
was not a valid Unicode codepoint.
IllegalFormatConversionException The argument was the wrong
type for the conversion.
 
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