Serializable
, Cloneable
A
ChoiceFormat
allows you to attach a format to a range of numbers. It is generally used in a
MessageFormat
for handling plurals. The choice is specified with an ascending list of doubles, where each item specifies a half-open interval up to the next item:
X matches j if and only if limit[j] ≤ X < limit[j+1]
If there is no match, then either the first or last index is used, depending on whether the number (X) is too low or too high. If the limit array is not in ascending order, the results of formatting will be incorrect. ChoiceFormat also accepts
\u221E
as equivalent to infinity(INF).
Note: ChoiceFormat
differs from the other Format
classes in that you create a ChoiceFormat
object with a constructor (not with a getInstance
style factory method). The factory methods aren't necessary because ChoiceFormat
doesn't require any complex setup for a given locale. In fact, ChoiceFormat
doesn't implement any locale specific behavior.
When creating a ChoiceFormat
, you must specify an array of formats and an array of limits. The length of these arrays must be the same. For example,
nextDouble
can be used to get the next higher double, to make the half-open interval.)Here is a simple example that shows formatting and parsing:
double[] limits = {1,2,3,4,5,6,7}; String[] dayOfWeekNames = {"Sun","Mon","Tue","Wed","Thur","Fri","Sat"}; ChoiceFormat form = new ChoiceFormat(limits, dayOfWeekNames); ParsePosition status = new ParsePosition(0); for (double i = 0.0; i <= 8.0; ++i) { status.setIndex(0); System.out.println(i + " -> " + form.format(i) + " -> " + form.parse(form.format(i),status)); }
Here is a more complex example, with a pattern format:
double[] filelimits = {0,1,2}; String[] filepart = {"are no files","is one file","are {2} files"}; ChoiceFormat fileform = new ChoiceFormat(filelimits, filepart); Format[] testFormats = {fileform, null, NumberFormat.getInstance()}; MessageFormat pattform = new MessageFormat("There {0} on {1}"); pattform.setFormats(testFormats); Object[] testArgs = {null, "ADisk", null}; for (int i = 0; i < 4; ++i) { testArgs[0] = new Integer(i); testArgs[2] = testArgs[0]; System.out.println(pattform.format(testArgs)); }
Specifying a pattern for ChoiceFormat objects is fairly straightforward. For example:
ChoiceFormat fmt = new ChoiceFormat( "-1#is negative| 0#is zero or fraction | 1#is one |1.0<is 1+ |2#is two |2<is more than 2."); System.out.println("Formatter Pattern : " + fmt.toPattern()); System.out.println("Format with -INF : " + fmt.format(Double.NEGATIVE_INFINITY)); System.out.println("Format with -1.0 : " + fmt.format(-1.0)); System.out.println("Format with 0 : " + fmt.format(0)); System.out.println("Format with 0.9 : " + fmt.format(0.9)); System.out.println("Format with 1.0 : " + fmt.format(1)); System.out.println("Format with 1.5 : " + fmt.format(1.5)); System.out.println("Format with 2 : " + fmt.format(2)); System.out.println("Format with 2.1 : " + fmt.format(2.1)); System.out.println("Format with NaN : " + fmt.format(Double.NaN)); System.out.println("Format with +INF : " + fmt.format(Double.POSITIVE_INFINITY));
And the output result would be like the following:
SynchronizationFormat with -INF : is negative Format with -1.0 : is negative Format with 0 : is zero or fraction Format with 0.9 : is zero or fraction Format with 1.0 : is one Format with 1.5 : is 1+ Format with 2 : is two Format with 2.1 : is more than 2. Format with NaN : is negative Format with +INF : is more than 2.
Choice formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.
Constructors
Constructs with the limits and the corresponding formats.
Constructs with limits and corresponding formats based on the pattern.
void
boolean
Equality comparison between two
Returns pattern with formatted double.
Specialization of format.
Get the formats passed in the constructor.
double[]
Get the limits passed in the constructor.
int
Generates a hash code for the message format object.
static final double
Finds the least double greater than d
.
static double
Finds the least double greater than d
(if positive
is true
), or the greatest double less than d
(if positive
is false
).
Parses a Number from the input text.
static final double
Finds the greatest double less than d
.
void
Set the choices to be used in formatting.
Methods declared in class java.text.NumberFormatformat, format, format, getAvailableLocales, getCompactNumberInstance, getCompactNumberInstance, getCurrency, getCurrencyInstance, getCurrencyInstance, getInstance, getInstance, getIntegerInstance, getIntegerInstance, getMaximumFractionDigits, getMaximumIntegerDigits, getMinimumFractionDigits, getMinimumIntegerDigits, getNumberInstance, getNumberInstance, getPercentInstance, getPercentInstance, getRoundingMode, isGroupingUsed, isParseIntegerOnly, parse, parseObject, setCurrency, setGroupingUsed, setMaximumFractionDigits, setMaximumIntegerDigits, setMinimumFractionDigits, setMinimumIntegerDigits, setParseIntegerOnly, setRoundingMode
Constructs with limits and corresponding formats based on the pattern.
newPattern
- the new pattern string
NullPointerException
- if newPattern
is null
Constructs with the limits and the corresponding formats.
limits
- limits in ascending order
formats
- corresponding format strings
NullPointerException
- if limits
or formats
is null
Sets the pattern.
newPattern
- See the class description.
NullPointerException
- if newPattern
is null
Gets the pattern.
Set the choices to be used in formatting.
limits
- contains the top value that you want parsed with that format, and should be in ascending sorted order. When formatting X, the choice will be the i, where limit[i] ≤ X < limit[i+1]. If the limit array is not in ascending order, the results of formatting will be incorrect.
formats
- are the formats you want to use for each limit. They can be either Format objects or Strings. When formatting with object Y, if the object is a NumberFormat, then ((NumberFormat) Y).format(X) is called. Otherwise Y.toString() is called.
NullPointerException
- if limits
or formats
is null
public double[] getLimits()
Get the limits passed in the constructor.
Get the formats passed in the constructor.
Specialization of format. This method really calls format(double, StringBuffer, FieldPosition)
thus the range of longs that are supported is only equal to the range that can be stored by double. This will never be a practical limitation.
format
in class NumberFormat
number
- the long number to format
toAppendTo
- the StringBuffer to which the formatted text is to be appended
status
- keeps track on the position of the field within the returned string. For example, for formatting a number 123456789
in Locale.US
locale, if the given fieldPosition
is NumberFormat.INTEGER_FIELD
, the begin index and end index of fieldPosition
will be set to 0 and 11, respectively for the output string 123,456,789
.
Returns pattern with formatted double.
format
in class NumberFormat
number
- number to be formatted and substituted.
toAppendTo
- where text is appended.
status
- ignore no useful status is returned.
NullPointerException
- if toAppendTo
is null
Parses a Number from the input text.
parse
in class NumberFormat
text
- the source text.
status
- an input-output parameter. On input, the status.index field indicates the first character of the source text that should be parsed. On exit, if no error occurred, status.index is set to the first unparsed character in the source text. On exit, if an error did occur, status.index is unchanged and status.errorIndex is set to the first index of the character that caused the parse to fail.
NullPointerException
- if status
is null
or if text
is null
and the list of choice strings is not empty.
public static final double nextDouble(double d)
Finds the least double greater than
d
. If
NaN
, returns same value.
Used to make half-open intervals.
Math.nextUp(d)
d
- the reference value
d
public static final double previousDouble(double d)
Finds the greatest double less than d
. If NaN
, returns same value.
Math.nextDown(d)
d
- the reference value
d
Overrides Cloneable
clone
in class NumberFormat
public int hashCode()
Generates a hash code for the message format object.
hashCode
in class NumberFormat
Equality comparison between two
equals
in class NumberFormat
obj
- the reference object with which to compare.
true
if this object is the same as the obj argument; false
otherwise.
public static double nextDouble(double d, boolean positive)
Finds the least double greater than d
(if positive
is true
), or the greatest double less than d
(if positive
is false
). If NaN
, returns same value.
positive ? Math.nextUp(d) : Math.nextDown(d)
d
- the reference value
positive
- true
if the least double is desired; false
otherwise
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