Number Format Pattern Syntax

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Trail: Learning the Java Language
Lesson: Object Basics and Simple Data Objects

Number Format Pattern Syntax

You can design your own format patterns for numbers by following the rules specified by the following BNF diagram:
pattern    := subpattern{;subpattern}
subpattern := {prefix}integer{.fraction}{suffix}
prefix     := '\\u0000'..'\\uFFFD' - specialCharacters
suffix     := '\\u0000'..'\\uFFFD' - specialCharacters
integer    := '#'* '0'* '0'
fraction   := '0'* '#'*
The notation used in the preceding diagram is explained in the following table:
Notation Description
X*
0 or more instances of X
(X | Y)
either X or Y
X..Y
any character from X up to Y, inclusive
S - T
characters in S, except those in T
{X}
X is optional
In the preceding BNF diagram, the first subpattern specifies the format for positive numbers. The second subpattern, which is optional, specifies the format for negative numbers.
Although not noted in the BNF diagram, a comma may appear within the integer portion.
Within the subpatterns, you specify formatting with special symbols. These symbols are described in the following table:

Symbol Description

0 a digit

# a digit, zero shows as absent

. placeholder for decimal separator

, placeholder for grouping separator

E separates mantissa and exponent for exponential formats

; separates formats

- default negative prefix

% multiply by 100 and show as percentage

? multiply by 1000 and show as per mille

¤ currency sign; replaced by currency symbol; if doubled, replaced by international currency symbol; if present in a pattern, the monetary decimal separator is used instead of the decimal separator

X any other characters can be used in the prefix or suffix

' used to quote special characters in a prefix or suffix

Notation	Description
X*	0 or more instances of X
(X \| Y)	either X or Y
X..Y	any character from X up to Y, inclusive
S - T	characters in S, except those in T
{X}	X is optional

Symbol	Description
0	a digit
#	a digit, zero shows as absent
.	placeholder for decimal separator
,	placeholder for grouping separator
E	separates mantissa and exponent for exponential formats
;	separates formats
-	default negative prefix
%	multiply by 100 and show as percentage
?	multiply by 1000 and show as per mille
¤	currency sign; replaced by currency symbol; if doubled, replaced by international currency symbol; if present in a pattern, the monetary decimal separator is used instead of the decimal separator
X	any other characters can be used in the prefix or suffix
'	used to quote special characters in a prefix or suffix

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