## Patterns for Integers and Floating Point Numbers

Number patterns support different kinds of numbers, including integers (123), fixed-point numbers (123.4), scientific notation (1.23E4), percentages (12%), and currency amounts (\$123). All of these can be localized.

A number pattern contains a postive and negative subpattern, for example, "#,##0.00;(#,##0.00)". Each subpattern has a prefix, numeric part, and suffix. The negative subpattern is optional; if absent, then the positive subpattern prefixed with the localized minus sign ('-' in most locales) is used as the negative subpattern. That is, "0.00" alone is equivalent to "0.00;-0.00". If there is an explicit negative subpattern, it serves only to specify the negative prefix and suffix; the number of digits, minimal digits, and other characteristics are all the same as the positive pattern. That means that "#,##0.0#;(#)" produces precisely the same behavior as "#,##0.0#;(#,##0.0#)".

## Special Pattern Characters

Most characters in a pattern are taken literally; they are matched during parsing and output unchanged during formatting. Special characters, on the other hand, stand for other characters, strings, or classes of characters. They must be quoted, unless noted otherwise, if they are to appear in the prefix or suffix as literals.

The characters listed here are used in non-localized patterns. Localized patterns use the corresponding characters from the locale instead, and these characters lose their special status. Two exceptions are the currency sign and quote, which are not localized.

Symbol Location Localized? Meaning
0 Number Y Digit
# Number Y Digit, zero shows as absent
. Number Y Decimal separator or monetary decimal separator
- Number Y Minus sign
, Number Y Grouping separator
E Number Y Separates mantissa and exponent in scientific notation. Need not be quoted in prefix or suffix.
; Subpattern boundary Y Separates positive and negative subpatterns
% Prefix or suffix Y Multiply by 100 and show as percentage
\u2030 Prefix or suffix Y Multiply by 1000 and show as per mille
¤
(\u00A4)
Prefix or suffix N 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.
' Prefix or suffix N Used to quote special characters in a prefix or suffix, for example, `"'#'#"` formats 123 to `"#123"`. To create a single quote itself, use two in a row: ```"# o''clock"```.

## Scientific Notation

Numbers in scientific notation are expressed as the product of a mantissa and a power of ten, for example, 1234 can be expressed as 1.234 x 10^3. The mantissa is often in the range 1.0 <=x < 10.0, but it need not be. `DecimalFormat` can be instructed to format and parse scientific notation only via a pattern; there is currently no factory method that creates a scientific notation format. In a pattern, the exponent character immediately followed by one or more digit characters indicates scientific notation. Example: "0.###E0" formats the number 1234 as "1.234E3".

• The number of digit characters after the exponent character gives the minimum exponent digit count. There is no maximum. Negative exponents are formatted using the localized minus sign, not the prefix and suffix from the pattern. This allows patterns such as "0.###E0 m/s".
• The minimum number of integer digits is achieved by adjusting the exponent. Example: 0.00123 formatted with "00.###E0" yields "12.3E-4". This only happens if there is no maximum number of integer digits. If there is a maximum, then the minimum number of integer digits is fixed at one.
• The maximum number of integer digits, if present, forces the exponent to be a multiple of that number. The most common use of this is to generate engineering notation, in which the exponent is a multiple of three, e.g., "##0.#####E0". Using this pattern, the number 12345 formats to "12.345E3", and 123456 formats to "123.456E3".
• The number of significant digits in the mantissa is the sum of the minimum integer and maximum fraction digits, and is unaffected by the maximum integer digits. For example, 12345 formatted with "##0.##E0" is "12.3E3". To show all digits, set the significant digits count to zero. The number of significant digits does not affect parsing.
• Exponential patterns may not contain grouping separators.

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