Closeable, Flushable, AutoCloseablepublic final class Formatter extends Object implements Closeable, Flushable
byte, BigDecimal, and Calendar
are supported. Limited formatting customization for arbitrary user types is
provided through the Formattable interface.
Formatters are not necessarily safe for multithreaded access. Thread safety is optional and is the responsibility of users of methods in this class.
Formatted printing for the Java language is heavily inspired by C's
printf. Although the format strings are similar to C, some
customizations have been made to accommodate the Java language and exploit
some of its features. Also, Java formatting is more strict than C's; for
example, if a conversion is incompatible with a flag, an exception will be
thrown. In C inapplicable flags are silently ignored. The format strings
are thus intended to be recognizable to C programmers but not necessarily
completely compatible with those in C.
Examples of expected usage:
StringBuilder sb = new StringBuilder();
// Send all output to the Appendable object sb
Formatter formatter = new Formatter(sb, Locale.US);
// Explicit argument indices may be used to re-order output.
formatter.format("%4$2s %3$2s %2$2s %1$2s", "a", "b", "c", "d")
// -> " d c b a"
// Optional locale as the first argument can be used to get
// locale-specific formatting of numbers. The precision and width can be
// given to round and align the value.
formatter.format(Locale.FRANCE, "e = %+10.4f", Math.E);
// -> "e = +2,7183"
// The '(' numeric flag may be used to format negative numbers with
// parentheses rather than a minus sign. Group separators are
// automatically inserted.
formatter.format("Amount gained or lost since last statement: $ %(,.2f",
balanceDelta);
// -> "Amount gained or lost since last statement: $ (6,217.58)"
Convenience methods for common formatting requests exist as illustrated by the following invocations:
// Writes a formatted string to System.out.
System.out.format("Local time: %tT", Calendar.getInstance());
// -> "Local time: 13:34:18"
// Writes formatted output to System.err.
System.err.printf("Unable to open file '%1$s': %2$s",
fileName, exception.getMessage());
// -> "Unable to open file 'food': No such file or directory"
Like C's sprintf(3), Strings may be formatted using the static
method String#format(String,Object...):
// Format a string containing a date.
import java.util.Calendar;
import java.util.GregorianCalendar;
import static java.util.Calendar.*;
Calendar c = new GregorianCalendar(1995, MAY, 23);
String s = String.format("Duke's Birthday: %1$tb %1$te, %1$tY", c);
// -> s == "Duke's Birthday: May 23, 1995"
This specification is divided into two sections. The first section, Summary, covers the basic formatting concepts. This section is intended for users who want to get started quickly and are familiar with formatted printing in other programming languages. The second section, Details, covers the specific implementation details. It is intended for users who want more precise specification of formatting behavior.
This section is intended to provide a brief overview of formatting concepts. For precise behavioral details, refer to the Details section.
Every method which produces formatted output requires a format
string and an argument list. The format string is a String which may contain fixed text and one or more embedded format
specifiers. Consider the following example:
Calendar c = ...;
String s = String.format("Duke's Birthday: %1$tm %1$te,%1$tY", c);
format method. It
contains three format specifiers "%1$tm", "%1$te", and
"%1$tY" which indicate how the arguments should be processed and
where they should be inserted in the text. The remaining portions of the
format string are fixed text including "Dukes Birthday: " and any
other spaces or punctuation.
The argument list consists of all arguments passed to the method after the
format string. In the above example, the argument list is of size one and
consists of the Calendar object c.
%[argument_index$][flags][width][.precision]conversion
The optional argument_index is a decimal integer indicating the
position of the argument in the argument list. The first argument is
referenced by "1$", the second by "2$", etc.
The optional flags is a set of characters that modify the output format. The set of valid flags depends on the conversion.
The optional width is a positive decimal integer indicating the minimum number of characters to be written to the output.
The optional precision is a non-negative decimal integer usually used to restrict the number of characters. The specific behavior depends on the conversion.
The required conversion is a character indicating how the argument should be formatted. The set of valid conversions for a given argument depends on the argument's data type.
%[argument_index$][flags][width]conversion
The optional argument_index, flags and width are defined as above.
The required conversion is a two character sequence. The first
character is 't' or 'T'. The second character indicates
the format to be used. These characters are similar to but not completely
identical to those defined by GNU date and POSIX
strftime(3c).
%[flags][width]conversion
The optional flags and width is defined as above.
The required conversion is a character indicating content to be inserted in the output.
Conversions are divided into the following categories:
char, Character, byte, Byte, short, and Short. This conversion may also be
applied to the types int and Integer when Character#isValidCodePoint returns true
byte,
Byte, short, Short, int and Integer, long, Long, and BigInteger (but not char or Character)
float, Float, double, Double, and BigDecimal
long, Long, Calendar,
Date and TemporalAccessor
'%'
('\u0025')
The following table summarizes the supported conversions. Conversions
denoted by an upper-case character (i.e. 'B', 'H',
'S', 'C', 'X', 'E', 'G',
'A', and 'T') are the same as those for the corresponding
lower-case conversion characters except that the result is converted to
upper case according to the rules of the prevailing Locale. The result is equivalent to the following invocation of String#toUpperCase()
out.toUpperCase()
| Conversion | Argument Category | Description |
|---|---|---|
'b', 'B'
| general | If the argument arg is null, then the result is
"false". If arg is a boolean or Boolean, then the result is the string returned by String#valueOf(boolean). Otherwise, the result is
"true".
|
'h', 'H'
| general | If the argument arg is null, then the result is
"null". Otherwise, the result is obtained by invoking
Integer.toHexString(arg.hashCode()).
|
's', 'S'
| general | If the argument arg is null, then the result is
"null". If arg implements Formattable, then
Formattable#formatTo is invoked. Otherwise, the
result is obtained by invoking arg.toString().
|
'c', 'C'
| character | The result is a Unicode character |
'd'
| integral | The result is formatted as a decimal integer |
'o'
| integral | The result is formatted as an octal integer |
'x', 'X'
| integral | The result is formatted as a hexadecimal integer |
'e', 'E'
| floating point | The result is formatted as a decimal number in computerized scientific notation |
'f'
| floating point | The result is formatted as a decimal number |
'g', 'G'
| floating point | The result is formatted using computerized scientific notation or decimal format, depending on the precision and the value after rounding. |
'a', 'A'
| floating point | The result is formatted as a hexadecimal floating-point number with
a significand and an exponent. This conversion is not supported
for the BigDecimal type despite the latter's being in the
floating point argument category.
|
't', 'T'
| date/time | Prefix for date and time conversion characters. See Date/Time Conversions. |
'%'
| percent | The result is a literal '%' ('\u0025')
|
'n'
| line separator | The result is the platform-specific line separator |
Any characters not explicitly defined as conversions are illegal and are reserved for future extensions.
The following date and time conversion suffix characters are defined for
the 't' and 'T' conversions. The types are similar to but
not completely identical to those defined by GNU date and POSIX
strftime(3c). Additional conversion types are provided to access
Java-specific functionality (e.g. 'L' for milliseconds within the
second).
The following conversion characters are used for formatting times:
'H'
| Hour of the day for the 24-hour clock, formatted as two digits with
a leading zero as necessary i.e. 00 - 23.
|
'I'
| Hour for the 12-hour clock, formatted as two digits with a leading
zero as necessary, i.e. 01 - 12.
|
'k'
| Hour of the day for the 24-hour clock, i.e. 0 - 23.
|
'l'
| Hour for the 12-hour clock, i.e. 1 - 12.
|
'M'
| Minute within the hour formatted as two digits with a leading zero
as necessary, i.e. 00 - 59.
|
'S'
| Seconds within the minute, formatted as two digits with a leading
zero as necessary, i.e. 00 - 60 ("60" is a special
value required to support leap seconds).
|
'L'
| Millisecond within the second formatted as three digits with
leading zeros as necessary, i.e. 000 - 999.
|
'N'
| Nanosecond within the second, formatted as nine digits with leading
zeros as necessary, i.e. 000000000 - 999999999.
|
'p'
| Locale-specific morning or afternoon marker
in lower case, e.g."am" or "pm". Use of the conversion
prefix 'T' forces this output to upper case.
|
'z'
| RFC 822
style numeric time zone offset from GMT, e.g. -0800. This
value will be adjusted as necessary for Daylight Saving Time. For
long, Long, and Date the time zone used is
the TimeZone#getDefault() for this
instance of the Java virtual machine.
|
'Z'
| A string representing the abbreviation for the time zone. This
value will be adjusted as necessary for Daylight Saving Time. For
long, Long, and Date the time zone used is
the TimeZone#getDefault() for this
instance of the Java virtual machine. The Formatter's locale will
supersede the locale of the argument (if any).
|
's'
| Seconds since the beginning of the epoch starting at 1 January 1970
00:00:00 UTC, i.e. Long.MIN_VALUE/1000 to
Long.MAX_VALUE/1000.
|
'Q'
| Milliseconds since the beginning of the epoch starting at 1 January
1970 00:00:00 UTC, i.e. Long.MIN_VALUE to
Long.MAX_VALUE.
|
The following conversion characters are used for formatting dates:
'B'
| Locale-specific full month name, e.g. "January", "February".
|
'b'
| Locale-specific abbreviated month name,
e.g. "Jan", "Feb".
|
'h'
| Same as 'b'.
|
'A'
| Locale-specific full name of the day of the week,
e.g. "Sunday", "Monday"
|
'a'
| Locale-specific short name of the day of the week,
e.g. "Sun", "Mon"
|
'C'
| Four-digit year divided by 100, formatted as two digits
with leading zero as necessary, i.e. 00 - 99
|
'Y'
| Year, formatted as at least four digits with leading zeros as
necessary, e.g. 0092 equals 92 CE for the Gregorian
calendar.
|
'y'
| Last two digits of the year, formatted with leading zeros as
necessary, i.e. 00 - 99.
|
'j'
| Day of year, formatted as three digits with leading zeros as
necessary, e.g. 001 - 366 for the Gregorian calendar.
|
'm'
| Month, formatted as two digits with leading zeros as necessary,
i.e. 01 - 13.
|
'd'
| Day of month, formatted as two digits with leading zeros as
necessary, i.e. 01 - 31
|
'e'
| Day of month, formatted as two digits, i.e. 1 - 31.
|
The following conversion characters are used for formatting common date/time compositions.
'R'
| Time formatted for the 24-hour clock as "%tH:%tM"
|
'T'
| Time formatted for the 24-hour clock as "%tH:%tM:%tS".
|
'r'
| Time formatted for the 12-hour clock as "%tI:%tM:%tS %Tp".
The location of the morning or afternoon marker ('%Tp') may be
locale-dependent.
|
'D'
| Date formatted as "%tm/%td/%ty".
|
'F'
| ISO 8601
complete date formatted as "%tY-%tm-%td".
|
'c'
| Date and time formatted as "%ta %tb %td %tT %tZ %tY",
e.g. "Sun Jul 20 16:17:00 EDT 1969".
|
Any characters not explicitly defined as date/time conversion suffixes are illegal and are reserved for future extensions.
The following table summarizes the supported flags. y means the flag is supported for the indicated argument types.
| Flag | General | Character | Integral | Floating Point | Date/Time | Description |
|---|---|---|---|---|---|---|
| '-' | y | y | y | y | y | The result will be left-justified. |
| '#' | y1 | - | y3 | y | - | The result should use a conversion-dependent alternate form |
| '+' | - | - | y4 | y | - | The result will always include a sign |
| ' ' | - | - | y4 | y | - | The result will include a leading space for positive values |
| '0' | - | - | y | y | - | The result will be zero-padded |
| ',' | - | - | y2 | y5 | - | The result will include locale-specific grouping separators |
| '(' | - | - | y4 | y5 | - | The result will enclose negative numbers in parentheses |
1 Depends on the definition of Formattable.
2 For 'd' conversion only.
3 For 'o', 'x', and 'X'
conversions only.
4 For 'd', 'o', 'x', and
'X' conversions applied to BigInteger
or 'd' applied to byte, Byte, short, Short, int and Integer, long, and Long.
5 For 'e', 'E', 'f',
'g', and 'G' conversions only.
Any characters not explicitly defined as flags are illegal and are reserved for future extensions.
The width is the minimum number of characters to be written to the output. For the line separator conversion, width is not applicable; if it is provided, an exception will be thrown.
For general argument types, the precision is the maximum number of characters to be written to the output.
For the floating-point conversions 'a', 'A', 'e',
'E', and 'f' the precision is the number of digits after the
radix point. If the conversion is 'g' or 'G', then the
precision is the total number of digits in the resulting magnitude after
rounding.
For character, integral, and date/time argument types and the percent and line separator conversions, the precision is not applicable; if a precision is provided, an exception will be thrown.
The argument index is a decimal integer indicating the position of the
argument in the argument list. The first argument is referenced by
"1$", the second by "2$", etc.
Another way to reference arguments by position is to use the
'<' ('\u003c') flag, which causes the argument for
the previous format specifier to be re-used. For example, the following two
statements would produce identical strings:
Calendar c = ...;
String s1 = String.format("Duke's Birthday: %1$tm %1$te,%1$tY", c);
String s2 = String.format("Duke's Birthday: %1$tm %<te,%<tY", c);
This section is intended to provide behavioral details for formatting, including conditions and exceptions, supported data types, localization, and interactions between flags, conversions, and data types. For an overview of formatting concepts, refer to the Summary
Any characters not explicitly defined as conversions, date/time
conversion suffixes, or flags are illegal and are reserved for
future extensions. Use of such a character in a format string will
cause an UnknownFormatConversionException or UnknownFormatFlagsException to be thrown.
If the format specifier contains a width or precision with an invalid
value or which is otherwise unsupported, then a IllegalFormatWidthException or IllegalFormatPrecisionException
respectively will be thrown.
If a format specifier contains a conversion character that is not
applicable to the corresponding argument, then an IllegalFormatConversionException will be thrown.
All specified exceptions may be thrown by any of the format
methods of Formatter as well as by any format convenience
methods such as String#format(String,Object...) and
PrintStream.printf.
Conversions denoted by an upper-case character (i.e. 'B',
'H', 'S', 'C', 'X', 'E',
'G', 'A', and 'T') are the same as those for the
corresponding lower-case conversion characters except that the result is
converted to upper case according to the rules of the prevailing Locale. The result is equivalent to the following
invocation of String#toUpperCase()
out.toUpperCase()
The following general conversions may be applied to any argument type:
'b'
| '\u0062' | Produces either "true" or "false" as returned by
Boolean#toString(boolean).
If the argument is If the |
'B'
| '\u0042' | The upper-case variant of 'b'.
|
'h'
| '\u0068' | Produces a string representing the hash code value of the object.
If the argument, arg is If the |
'H'
| '\u0048' | The upper-case variant of 'h'.
|
's'
| '\u0073' | Produces a string.
If the argument is If the |
'S'
| '\u0053' | The upper-case variant of 's'.
|
The following flags apply to general conversions:
'-'
| '\u002d' | Left justifies the output. Spaces ('\u0020') will be
added at the end of the converted value as required to fill the minimum
width of the field. If the width is not provided, then a MissingFormatWidthException will be thrown. If this flag is not given
then the output will be right-justified.
|
'#'
| '\u0023' | Requires the output use an alternate form. The definition of the form is specified by the conversion. |
The width is the minimum number of characters to
be written to the
output. If the length of the converted value is less than the width then
the output will be padded by ' ' ('\u0020')
until the total number of characters equals the width. The padding is on
the left by default. If the '-' flag is given, then the padding
will be on the right. If the width is not specified then there is no
minimum.
The precision is the maximum number of characters to be written to the
output. The precision is applied before the width, thus the output will be
truncated to precision characters even if the width is greater than
the precision. If the precision is not specified then there is no explicit
limit on the number of characters.
char and Character. It
may also be applied to the types byte, Byte,
short, and Short, int and Integer when
Character#isValidCodePoint returns true. If it returns
false then an IllegalFormatCodePointException will be
thrown.
'c'
| '\u0063' | Formats the argument as a Unicode character as described in Unicode Character
Representation. This may be more than one 16-bit char in
the case where the argument represents a supplementary character.
If the |
'C'
| '\u0043' | The upper-case variant of 'c'.
|
The '-' flag defined for General
conversions applies. If the '#' flag is given, then a FormatFlagsConversionMismatchException will be thrown.
The width is defined as for General conversions.
The precision is not applicable. If the precision is specified then an
IllegalFormatPrecisionException will be thrown.
Numeric conversions are divided into the following categories:
Numeric types will be formatted according to the following algorithm:
After digits are obtained for the integer part, fractional part, and exponent (as appropriate for the data type), the following transformation is applied:
'0'
+ z.
',' ('\u002c')
flag is given, then the locale-specific grouping separator is
inserted by scanning the integer part of the string from least significant
to most significant digits and inserting a separator at intervals defined by
the locale's grouping
size.
'0' flag is given, then the locale-specific zero digits are inserted
after the sign character, if any, and before the first non-zero digit, until
the length of the string is equal to the requested field width.
'(' flag is given, then a
'(' ('\u0028') is prepended and a ')'
('\u0029') is appended.
'(' flag is not given, then a '-' ('\u002d')
is prepended.
'+' flag is given and the value is positive or zero (or
floating-point positive zero), then a '+' ('\u002b')
will be prepended.
If the value is NaN or positive infinity the literal strings "NaN" or
"Infinity" respectively, will be output. If the value is negative infinity,
then the output will be "(Infinity)" if the '(' flag is given
otherwise the output will be "-Infinity". These values are not localized.
Byte, Short, Integer, and Long
The following conversions may be applied to byte, Byte,
short, Short, int and Integer,
long, and Long.
'd'
| '\u0064' | Formats the argument as a decimal integer. The localization algorithm is applied.
If the If the |
'o'
| '\u006f' | Formats the argument as an integer in base eight. No localization
is applied.
If x is negative then the result will be an unsigned value
generated by adding 2n to the value where If the If the If |
'x'
| '\u0078' | Formats the argument as an integer in base sixteen. No
localization is applied.
If x is negative then the result will be an unsigned value
generated by adding 2n to the value where If the If the If |
'X'
| '\u0058' | The upper-case variant of 'x'. The entire string
representing the number will be converted to String#toUpperCase including the 'x' (if any) and
all hexadecimal digits 'a' - 'f'
('\u0061' - '\u0066').
|
If the conversion is 'o', 'x', or 'X' and
both the '#' and the '0' flags are given, then result will
contain the radix indicator ('0' for octal and "0x" or
"0X" for hexadecimal), some number of zeros (based on the width),
and the value.
If the '-' flag is not given, then the space padding will occur
before the sign.
The following flags apply to numeric integral conversions:
'+'
| '\u002b' | Requires the output to include a positive sign for all positive
numbers. If this flag is not given then only negative values will
include a sign.
If both the |
| ' ' | '\u0020' | Requires the output to include a single extra space
('\u0020') for non-negative values.
If both the |
'0'
| '\u0030' | Requires the output to be padded with leading zeros to the minimum field
width following any sign or radix indicator except when converting NaN
or infinity. If the width is not provided, then a MissingFormatWidthException will be thrown.
If both the |
','
| '\u002c' | Requires the output to include the locale-specific group separators as described in the "group" section of the localization algorithm. |
'('
| '\u0028' | Requires the output to prepend a '('
('\u0028') and append a ')'
('\u0029') to negative values.
|
If no flags are given the default formatting is as follows:
width
'-' ('\u002d')
The width is the minimum number of characters to
be written to the output. This includes any signs, digits, grouping
separators, radix indicator, and parentheses. If the length of the
converted value is less than the width then the output will be padded by
spaces ('\u0020') until the total number of characters equals
width. The padding is on the left by default. If '-' flag is
given then the padding will be on the right. If width is not specified then
there is no minimum.
The precision is not applicable. If precision is specified then an
IllegalFormatPrecisionException will be thrown.
The following conversions may be applied to BigInteger.
'd'
| '\u0064' | Requires the output to be formatted as a decimal integer. The localization algorithm is applied.
If the |
'o'
| '\u006f' | Requires the output to be formatted as an integer in base eight.
No localization is applied.
If x is negative then the result will be a signed value
beginning with If x is positive or zero and the If the If the If the |
'x'
| '\u0078' | Requires the output to be formatted as an integer in base
sixteen. No localization is applied.
If x is negative then the result will be a signed value
beginning with If x is positive or zero and the If the If the If the |
'X'
| '\u0058' | The upper-case variant of 'x'. The entire string
representing the number will be converted to String#toUpperCase including the 'x' (if any) and
all hexadecimal digits 'a' - 'f'
('\u0061' - '\u0066').
|
If the conversion is 'o', 'x', or 'X' and
both the '#' and the '0' flags are given, then result will
contain the base indicator ('0' for octal and "0x" or
"0X" for hexadecimal), some number of zeros (based on the width),
and the value.
If the '0' flag is given and the value is negative, then the
zero padding will occur after the sign.
If the '-' flag is not given, then the space padding will occur
before the sign.
All flags defined for Byte, Short, Integer, and Long apply. The default behavior when no flags are given is the same as for Byte, Short, Integer, and Long.
The specification of width is the same as defined for Byte, Short, Integer, and Long.
The precision is not applicable. If precision is specified then an
IllegalFormatPrecisionException will be thrown.
The following conversions may be applied to float, Float, double and Double.
'e'
| '\u0065' | Requires the output to be formatted using computerized scientific notation. The localization algorithm is applied.
The formatting of the magnitude m depends upon its value. If m is NaN or infinite, the literal strings "NaN" or "Infinity", respectively, will be output. These values are not localized. If m is positive-zero or negative-zero, then the exponent
will be Otherwise, the result is a string that represents the sign and magnitude (absolute value) of the argument. The formatting of the sign is described in the localization algorithm. The formatting of the magnitude m depends upon its value. Let n be the unique integer such that 10n
<= m < 10n+1; then let a be the
mathematically exact quotient of m and 10n so
that 1 <= a < 10. The magnitude is then represented as the
integer part of a, as a single decimal digit, followed by the
decimal separator followed by decimal digits representing the fractional
part of a, followed by the exponent symbol The number of digits in the result for the fractional part of
m or a is equal to the precision. If the precision is not
specified then the default value is If the |
'E'
| '\u0045' | The upper-case variant of 'e'. The exponent symbol
will be 'E' ('\u0045').
|
'g'
| '\u0067' | Requires the output to be formatted in general scientific notation
as described below. The localization
algorithm is applied.
After rounding for the precision, the formatting of the resulting magnitude m depends on its value. If m is greater than or equal to 10-4 but less than 10precision then it is represented in decimal format. If m is less than 10-4 or greater than or equal to 10precision, then it is represented in computerized scientific notation. The total number of significant digits in m is equal to the
precision. If the precision is not specified, then the default value is
If the |
'G'
| '\u0047' | The upper-case variant of 'g'.
|
'f'
| '\u0066' | Requires the output to be formatted using decimal
format. The localization algorithm is
applied.
The result is a string that represents the sign and magnitude (absolute value) of the argument. The formatting of the sign is described in the localization algorithm. The formatting of the magnitude m depends upon its value. If m NaN or infinite, the literal strings "NaN" or "Infinity", respectively, will be output. These values are not localized. The magnitude is formatted as the integer part of m, with no leading zeroes, followed by the decimal separator followed by one or more decimal digits representing the fractional part of m. The number of digits in the result for the fractional part of
m or a is equal to the precision. If the precision is not
specified then the default value is |
'a'
| '\u0061' | Requires the output to be formatted in hexadecimal exponential
form. No localization is applied.
The result is a string that represents the sign and magnitude (absolute value) of the argument x. If x is negative or a negative-zero value then the result
will begin with If x is positive or a positive-zero value and the
The formatting of the magnitude m depends upon its value.
If the |
'A'
| '\u0041' | The upper-case variant of 'a'. The entire string
representing the number will be converted to upper case including the
'x' ('\u0078') and 'p'
('\u0070' and all hexadecimal digits 'a' -
'f' ('\u0061' - '\u0066').
|
All flags defined for Byte, Short, Integer, and Long apply.
If the '#' flag is given, then the decimal separator will
always be present.
If no flags are given the default formatting is as follows:
width
'-'
The width is the minimum number of characters
to be written to the output. This includes any signs, digits, grouping
separators, decimal separators, exponential symbol, radix indicator,
parentheses, and strings representing infinity and NaN as applicable. If
the length of the converted value is less than the width then the output
will be padded by spaces ('\u0020') until the total number of
characters equals width. The padding is on the left by default. If the
'-' flag is given then the padding will be on the right. If width
is not specified then there is no minimum.
If the conversion is 'e',
'E' or 'f', then the precision is the number of digits
after the decimal separator. If the precision is not specified, then it is
assumed to be 6.
If the conversion is 'g' or 'G', then the precision is
the total number of significant digits in the resulting magnitude after
rounding. If the precision is not specified, then the default value is
6. If the precision is 0, then it is taken to be
1.
If the conversion is 'a' or 'A', then the precision
is the number of hexadecimal digits after the radix point. If the
precision is not provided, then all of the digits as returned by Double#toHexString(double) will be output.
The following conversions may be applied BigDecimal.
'e'
| '\u0065' | Requires the output to be formatted using computerized scientific notation. The localization algorithm is applied.
The formatting of the magnitude m depends upon its value. If m is positive-zero or negative-zero, then the exponent
will be Otherwise, the result is a string that represents the sign and magnitude (absolute value) of the argument. The formatting of the sign is described in the localization algorithm. The formatting of the magnitude m depends upon its value. Let n be the unique integer such that 10n
<= m < 10n+1; then let a be the
mathematically exact quotient of m and 10n so
that 1 <= a < 10. The magnitude is then represented as the
integer part of a, as a single decimal digit, followed by the
decimal separator followed by decimal digits representing the fractional
part of a, followed by the exponent symbol The number of digits in the result for the fractional part of
m or a is equal to the precision. If the precision is not
specified then the default value is If the |
'E'
| '\u0045' | The upper-case variant of 'e'. The exponent symbol
will be 'E' ('\u0045').
|
'g'
| '\u0067' | Requires the output to be formatted in general scientific notation
as described below. The localization
algorithm is applied.
After rounding for the precision, the formatting of the resulting magnitude m depends on its value. If m is greater than or equal to 10-4 but less than 10precision then it is represented in decimal format. If m is less than 10-4 or greater than or equal to 10precision, then it is represented in computerized scientific notation. The total number of significant digits in m is equal to the
precision. If the precision is not specified, then the default value is
If the |
'G'
| '\u0047' | The upper-case variant of 'g'.
|
'f'
| '\u0066' | Requires the output to be formatted using decimal
format. The localization algorithm is
applied.
The result is a string that represents the sign and magnitude (absolute value) of the argument. The formatting of the sign is described in the localization algorithm. The formatting of the magnitude m depends upon its value. The magnitude is formatted as the integer part of m, with no leading zeroes, followed by the decimal separator followed by one or more decimal digits representing the fractional part of m. The number of digits in the result for the fractional part of
m or a is equal to the precision. If the precision is not
specified then the default value is |
All flags defined for Byte, Short, Integer, and Long apply.
If the '#' flag is given, then the decimal separator will
always be present.
The default behavior when no flags are given is the same as for Float and Double.
The specification of width and precision is the same as defined for Float and Double.
This conversion may be applied to long, Long, Calendar, Date and TemporalAccessor
't'
| '\u0074' | Prefix for date and time conversion characters. |
'T'
| '\u0054' | The upper-case variant of 't'.
|
The following date and time conversion character suffixes are defined
for the 't' and 'T' conversions. The types are similar to
but not completely identical to those defined by GNU date and
POSIX strftime(3c). Additional conversion types are provided to
access Java-specific functionality (e.g. 'L' for milliseconds
within the second).
The following conversion characters are used for formatting times:
'H'
| '\u0048' | Hour of the day for the 24-hour clock, formatted as two digits with
a leading zero as necessary i.e. 00 - 23. 00
corresponds to midnight.
|
'I'
| '\u0049' | Hour for the 12-hour clock, formatted as two digits with a leading
zero as necessary, i.e. 01 - 12. 01 corresponds to
one o'clock (either morning or afternoon).
|
'k'
| '\u006b' | Hour of the day for the 24-hour clock, i.e. 0 - 23.
0 corresponds to midnight.
|
'l'
| '\u006c' | Hour for the 12-hour clock, i.e. 1 - 12. 1
corresponds to one o'clock (either morning or afternoon).
|
'M'
| '\u004d' | Minute within the hour formatted as two digits with a leading zero
as necessary, i.e. 00 - 59.
|
'S'
| '\u0053' | Seconds within the minute, formatted as two digits with a leading
zero as necessary, i.e. 00 - 60 ("60" is a special
value required to support leap seconds).
|
'L'
| '\u004c' | Millisecond within the second formatted as three digits with
leading zeros as necessary, i.e. 000 - 999.
|
'N'
| '\u004e' | Nanosecond within the second, formatted as nine digits with leading
zeros as necessary, i.e. 000000000 - 999999999. The precision
of this value is limited by the resolution of the underlying operating
system or hardware.
|
'p'
| '\u0070' | Locale-specific morning or afternoon marker
in lower case, e.g."am" or "pm". Use of the
conversion prefix 'T' forces this output to upper case. (Note
that 'p' produces lower-case output. This is different from
GNU date and POSIX strftime(3c) which produce
upper-case output.)
|
'z'
| '\u007a' | RFC 822
style numeric time zone offset from GMT, e.g. -0800. This
value will be adjusted as necessary for Daylight Saving Time. For
long, Long, and Date the time zone used is
the TimeZone#getDefault() for this
instance of the Java virtual machine.
|
'Z'
| '\u005a' | A string representing the abbreviation for the time zone. This
value will be adjusted as necessary for Daylight Saving Time. For
long, Long, and Date the time zone used is
the TimeZone#getDefault() for this
instance of the Java virtual machine. The Formatter's locale will
supersede the locale of the argument (if any).
|
's'
| '\u0073' | Seconds since the beginning of the epoch starting at 1 January 1970
00:00:00 UTC, i.e. Long.MIN_VALUE/1000 to
Long.MAX_VALUE/1000.
|
'Q'
| '\u004f' | Milliseconds since the beginning of the epoch starting at 1 January
1970 00:00:00 UTC, i.e. Long.MIN_VALUE to
Long.MAX_VALUE. The precision of this value is limited by
the resolution of the underlying operating system or hardware.
|
The following conversion characters are used for formatting dates:
'B'
| '\u0042' | Locale-specific full month name, e.g. "January", "February".
|
'b'
| '\u0062' | Locale-specific abbreviated month name,
e.g. "Jan", "Feb".
|
'h'
| '\u0068' | Same as 'b'.
|
'A'
| '\u0041' | Locale-specific full name of the day of the week,
e.g. "Sunday", "Monday"
|
'a'
| '\u0061' | Locale-specific short name of the day of the week,
e.g. "Sun", "Mon"
|
'C'
| '\u0043' | Four-digit year divided by 100, formatted as two digits
with leading zero as necessary, i.e. 00 - 99
|
'Y'
| '\u0059' | Year, formatted to at least
four digits with leading zeros as necessary, e.g. 0092 equals
92 CE for the Gregorian calendar.
|
'y'
| '\u0079' | Last two digits of the year, formatted with leading zeros as
necessary, i.e. 00 - 99.
|
'j'
| '\u006a' | Day of year, formatted as three digits with leading zeros as
necessary, e.g. 001 - 366 for the Gregorian calendar.
001 corresponds to the first day of the year.
|
'm'
| '\u006d' | Month, formatted as two digits with leading zeros as necessary,
i.e. 01 - 13, where "01" is the first month of the
year and ("13" is a special value required to support lunar
calendars).
|
'd'
| '\u0064' | Day of month, formatted as two digits with leading zeros as
necessary, i.e. 01 - 31, where "01" is the first day
of the month.
|
'e'
| '\u0065' | Day of month, formatted as two digits, i.e. 1 - 31 where
"1" is the first day of the month.
|
The following conversion characters are used for formatting common date/time compositions.
'R'
| '\u0052' | Time formatted for the 24-hour clock as "%tH:%tM"
|
'T'
| '\u0054' | Time formatted for the 24-hour clock as "%tH:%tM:%tS".
|
'r'
| '\u0072' | Time formatted for the 12-hour clock as "%tI:%tM:%tS
%Tp". The location of the morning or afternoon marker
('%Tp') may be locale-dependent.
|
'D'
| '\u0044' | Date formatted as "%tm/%td/%ty".
|
'F'
| '\u0046' | ISO 8601
complete date formatted as "%tY-%tm-%td".
|
'c'
| '\u0063' | Date and time formatted as "%ta %tb %td %tT %tZ %tY",
e.g. "Sun Jul 20 16:17:00 EDT 1969".
|
The '-' flag defined for General
conversions applies. If the '#' flag is given, then a FormatFlagsConversionMismatchException will be thrown.
The width is the minimum number of characters to
be written to the output. If the length of the converted value is less than
the width then the output will be padded by spaces
('\u0020') until the total number of characters equals width.
The padding is on the left by default. If the '-' flag is given
then the padding will be on the right. If width is not specified then there
is no minimum.
The precision is not applicable. If the precision is specified then an
IllegalFormatPrecisionException will be thrown.
The conversion does not correspond to any argument.
'%'
| The result is a literal '%' ('\u0025')
The width is the minimum number of characters to
be written to the output including the The The precision is not applicable. If the precision is specified an
|
The conversion does not correspond to any argument.
'n'
| the platform-specific line separator as returned by System#getProperty.
|
Flags, width, and precision are not applicable. If any are provided an
IllegalFormatFlagsException, IllegalFormatWidthException,
and IllegalFormatPrecisionException, respectively will be thrown.
Format specifiers can reference arguments in three ways:
1$", the second by "2$", etc. An argument
may be referenced more than once.
For example:
formatter.format("%4$s %3$s %2$s %1$s %4$s %3$s %2$s %1$s",
"a", "b", "c", "d")
// -> "d c b a d c b a"
'<' ('\u003c') flag which causes the argument for
the previous format specifier to be re-used. If there is no previous
argument, then a MissingFormatArgumentException is thrown.
formatter.format("%s %s %<s %<s", "a", "b", "c", "d")
// -> "a b b b"
// "c" and "d" are ignored because they are not referenced
'<' flag. Each format specifier
which uses ordinary indexing is assigned a sequential implicit index into
argument list which is independent of the indices used by explicit or
relative indexing.
formatter.format("%s %s %s %s", "a", "b", "c", "d")
// -> "a b c d"
It is possible to have a format string which uses all forms of indexing, for example:
formatter.format("%2$s %s %<s %s", "a", "b", "c", "d")
// -> "b a a b"
// "c" and "d" are ignored because they are not referenced
The maximum number of arguments is limited by the maximum dimension of a
Java array as defined by
The Java™ Virtual Machine Specification.
If the argument index is does not correspond to an
available argument, then a MissingFormatArgumentException is thrown.
If there are more arguments than format specifiers, the extra arguments are ignored.
Unless otherwise specified, passing a null argument to any
method or constructor in this class will cause a NullPointerException to be thrown.
| 限定符和类型 | 类 | 说明 |
|---|---|---|
static class |
Formatter.BigDecimalLayoutForm |
Enum for
BigDecimal formatting. |
| 构造器 | 说明 |
|---|---|
Formatter() |
Constructs a new formatter.
|
Formatter(File file) |
Constructs a new formatter with the specified file.
|
Formatter(File file,
String csn) |
Constructs a new formatter with the specified file and charset.
|
Formatter(File file,
String csn,
Locale l) |
Constructs a new formatter with the specified file, charset, and
locale.
|
Formatter(OutputStream os) |
Constructs a new formatter with the specified output stream.
|
Formatter(OutputStream os,
String csn) |
Constructs a new formatter with the specified output stream and
charset.
|
Formatter(OutputStream os,
String csn,
Locale l) |
Constructs a new formatter with the specified output stream, charset,
and locale.
|
Formatter(PrintStream ps) |
Constructs a new formatter with the specified print stream.
|
Formatter(Appendable a) |
Constructs a new formatter with the specified destination.
|
Formatter(Appendable a,
Locale l) |
Constructs a new formatter with the specified destination and locale.
|
Formatter(String fileName) |
Constructs a new formatter with the specified file name.
|
Formatter(String fileName,
String csn) |
Constructs a new formatter with the specified file name and charset.
|
Formatter(String fileName,
String csn,
Locale l) |
Constructs a new formatter with the specified file name, charset, and
locale.
|
Formatter(Locale l) |
Constructs a new formatter with the specified locale.
|
| 限定符和类型 | 方法 | 说明 |
|---|---|---|
void |
close() |
Closes this formatter.
|
void |
flush() |
Flushes this formatter.
|
Formatter |
format(String format,
Object... args) |
Writes a formatted string to this object's destination using the
specified format string and arguments.
|
Formatter |
format(Locale l,
String format,
Object... args) |
Writes a formatted string to this object's destination using the
specified locale, format string, and arguments.
|
IOException |
ioException() |
Returns the
IOException last thrown by this formatter's Appendable. |
Locale |
locale() |
Returns the locale set by the construction of this formatter.
|
Appendable |
out() |
Returns the destination for the output.
|
String |
toString() |
Returns the result of invoking
toString() on the destination
for the output. |
public Formatter()
The destination of the formatted output is a StringBuilder
which may be retrieved by invoking out() and whose
current content may be converted into a string by invoking toString(). The locale used is the Locale#getDefault(Locale.Category) for
Locale.Category#FORMAT for this instance of the Java
virtual machine.
public Formatter(Appendable a)
The locale used is the Locale#getDefault(Locale.Category) for Locale.Category#FORMAT for this instance of the Java virtual machine.
a - Destination for the formatted output. If a is
null then a StringBuilder will be created.public Formatter(Locale l)
The destination of the formatted output is a StringBuilder
which may be retrieved by invoking out() and whose current
content may be converted into a string by invoking toString().
l - The locale to apply during
formatting. If l is null then no localization
is applied.public Formatter(Appendable a, Locale l)
a - Destination for the formatted output. If a is
null then a StringBuilder will be created.l - The locale to apply during
formatting. If l is null then no localization
is applied.public Formatter(String fileName) throws FileNotFoundException
The charset used is the default charset for this instance of the Java virtual machine.
The locale used is the Locale#getDefault(Locale.Category) for Locale.Category#FORMAT for this instance of the Java virtual machine.
fileName - The name of the file to use as the destination of this
formatter. If the file exists then it will be truncated to
zero size; otherwise, a new file will be created. The output
will be written to the file and is buffered.SecurityException - If a security manager is present and SecurityManager#checkWrite denies write
access to the fileFileNotFoundException - If the given file name does not denote an existing, writable
regular file and a new regular file of that name cannot be
created, or if some other error occurs while opening or
creating the filepublic Formatter(String fileName, String csn) throws FileNotFoundException, UnsupportedEncodingException
The locale used is the Locale#getDefault(Locale.Category) for Locale.Category#FORMAT for this instance of the Java virtual machine.
fileName - The name of the file to use as the destination of this
formatter. If the file exists then it will be truncated to
zero size; otherwise, a new file will be created. The output
will be written to the file and is buffered.csn - The name of a supported charsetFileNotFoundException - If the given file name does not denote an existing, writable
regular file and a new regular file of that name cannot be
created, or if some other error occurs while opening or
creating the fileSecurityException - If a security manager is present and SecurityManager#checkWrite denies write
access to the fileUnsupportedEncodingException - If the named charset is not supportedpublic Formatter(String fileName, String csn, Locale l) throws FileNotFoundException, UnsupportedEncodingException
fileName - The name of the file to use as the destination of this
formatter. If the file exists then it will be truncated to
zero size; otherwise, a new file will be created. The output
will be written to the file and is buffered.csn - The name of a supported charsetl - The locale to apply during
formatting. If l is null then no localization
is applied.FileNotFoundException - If the given file name does not denote an existing, writable
regular file and a new regular file of that name cannot be
created, or if some other error occurs while opening or
creating the fileSecurityException - If a security manager is present and SecurityManager#checkWrite denies write
access to the fileUnsupportedEncodingException - If the named charset is not supportedpublic Formatter(File file) throws FileNotFoundException
The charset used is the default charset for this instance of the Java virtual machine.
The locale used is the Locale#getDefault(Locale.Category) for Locale.Category#FORMAT for this instance of the Java virtual machine.
file - The file to use as the destination of this formatter. If the
file exists then it will be truncated to zero size; otherwise,
a new file will be created. The output will be written to the
file and is buffered.SecurityException - If a security manager is present and SecurityManager#checkWrite denies
write access to the fileFileNotFoundException - If the given file object does not denote an existing, writable
regular file and a new regular file of that name cannot be
created, or if some other error occurs while opening or
creating the filepublic Formatter(File file, String csn) throws FileNotFoundException, UnsupportedEncodingException
The locale used is the Locale#getDefault(Locale.Category) for Locale.Category#FORMAT for this instance of the Java virtual machine.
file - The file to use as the destination of this formatter. If the
file exists then it will be truncated to zero size; otherwise,
a new file will be created. The output will be written to the
file and is buffered.csn - The name of a supported charsetFileNotFoundException - If the given file object does not denote an existing, writable
regular file and a new regular file of that name cannot be
created, or if some other error occurs while opening or
creating the fileSecurityException - If a security manager is present and SecurityManager#checkWrite denies
write access to the fileUnsupportedEncodingException - If the named charset is not supportedpublic Formatter(File file, String csn, Locale l) throws FileNotFoundException, UnsupportedEncodingException
file - The file to use as the destination of this formatter. If the
file exists then it will be truncated to zero size; otherwise,
a new file will be created. The output will be written to the
file and is buffered.csn - The name of a supported charsetl - The locale to apply during
formatting. If l is null then no localization
is applied.FileNotFoundException - If the given file object does not denote an existing, writable
regular file and a new regular file of that name cannot be
created, or if some other error occurs while opening or
creating the fileSecurityException - If a security manager is present and SecurityManager#checkWrite denies
write access to the fileUnsupportedEncodingException - If the named charset is not supportedpublic Formatter(PrintStream ps)
The locale used is the Locale#getDefault(Locale.Category) for Locale.Category#FORMAT for this instance of the Java virtual machine.
Characters are written to the given PrintStream object and are therefore encoded using that object's
charset.
ps - The stream to use as the destination of this formatter.public Formatter(OutputStream os)
The charset used is the default charset for this instance of the Java virtual machine.
The locale used is the Locale#getDefault(Locale.Category) for Locale.Category#FORMAT for this instance of the Java virtual machine.
os - The output stream to use as the destination of this formatter.
The output will be buffered.public Formatter(OutputStream os, String csn) throws UnsupportedEncodingException
The locale used is the Locale#getDefault(Locale.Category) for Locale.Category#FORMAT for this instance of the Java virtual machine.
os - The output stream to use as the destination of this formatter.
The output will be buffered.csn - The name of a supported charsetUnsupportedEncodingException - If the named charset is not supportedpublic Formatter(OutputStream os, String csn, Locale l) throws UnsupportedEncodingException
os - The output stream to use as the destination of this formatter.
The output will be buffered.csn - The name of a supported charsetl - The locale to apply during
formatting. If l is null then no localization
is applied.UnsupportedEncodingException - If the named charset is not supportedpublic Locale locale()
The format method
for this object which has a locale argument does not change this value.
null if no localization is applied, otherwise a
localeFormatterClosedException - If this formatter has been closed by invoking its close() methodpublic Appendable out()
FormatterClosedException - If this formatter has been closed by invoking its close() methodpublic String toString()
toString() on the destination
for the output. For example, the following code formats text into a
StringBuilder then retrieves the resultant string:
Formatter f = new Formatter();
f.format("Last reboot at %tc", lastRebootDate);
String s = f.toString();
// -> s == "Last reboot at Sat Jan 01 00:00:00 PST 2000"
An invocation of this method behaves in exactly the same way as the invocation
out().toString()
Depending on the specification of toString for the Appendable, the returned string may or may not contain the characters
written to the destination. For instance, buffers typically return
their contents in toString(), but streams cannot since the
data is discarded.
toString 在类中 ObjecttoString() on the destination
for the outputFormatterClosedException - If this formatter has been closed by invoking its close() methodpublic void flush()
Flushable interface, its flush method will be invoked.
Flushing a formatter writes any buffered output in the destination to the underlying stream.
flush 在接口中 FlushableFormatterClosedException - If this formatter has been closed by invoking its close() methodpublic void close()
Closeable interface, its close method will be invoked.
Closing a formatter allows it to release resources it may be holding (such as open files). If the formatter is already closed, then invoking this method has no effect.
Attempting to invoke any methods except ioException() in
this formatter after it has been closed will result in a FormatterClosedException.
close 在接口中 AutoCloseableclose 在接口中 Closeablepublic IOException ioException()
IOException last thrown by this formatter's Appendable.
If the destination's append() method never throws
IOException, then this method will always return null.
null if
no such exception exists.public Formatter format(String format, Object... args)
format - A format string as described in Format string
syntax.args - Arguments referenced by the format specifiers in the format
string. If there are more arguments than format specifiers, the
extra arguments are ignored. The maximum number of arguments is
limited by the maximum dimension of a Java array as defined by
The Java™ Virtual Machine Specification.IllegalFormatException - If a format string contains an illegal syntax, a format
specifier that is incompatible with the given arguments,
insufficient arguments given the format string, or other
illegal conditions. For specification of all possible
formatting errors, see the Details
section of the formatter class specification.FormatterClosedException - If this formatter has been closed by invoking its close() methodpublic Formatter format(Locale l, String format, Object... args)
l - The locale to apply during
formatting. If l is null then no localization
is applied. This does not change this object's locale that was
set during construction.format - A format string as described in Format string
syntaxargs - Arguments referenced by the format specifiers in the format
string. If there are more arguments than format specifiers, the
extra arguments are ignored. The maximum number of arguments is
limited by the maximum dimension of a Java array as defined by
The Java™ Virtual Machine Specification.IllegalFormatException - If a format string contains an illegal syntax, a format
specifier that is incompatible with the given arguments,
insufficient arguments given the format string, or other
illegal conditions. For specification of all possible
formatting errors, see the Details
section of the formatter class specification.FormatterClosedException - If this formatter has been closed by invoking its close() method