Class ChoiceFormat

java.text.ChoiceFormat

All Implemented Interfaces:: Serializable, Cloneable

public class ChoiceFormat extends NumberFormat

ChoiceFormat is a concrete subclass of NumberFormat that 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.

Patterns

A ChoiceFormat pattern has the following syntax:

Pattern:

SubPattern *("|" SubPattern)

SubPattern:

Limit Relation Format
_{Note: Each additional SubPattern must have an ascending Limit-Relation interval}

Limit:

Number / "∞" / "-∞"

Number:

["-"] *(Digit) 1*(Decimal / Digit) *(Digit) [Exponent]

Decimal:

1*(Digit ".") / 1*("." Digit)

Digit:

0 - 9

Exponent:

*(Digit) Digit ExponentSymbol Digit *(Digit)

ExponentSymbol:

"e" / "E"

Relation:

"#" / "<" / "≤"

Format:

Any characters except the special pattern character '|'

Note:The relation ≤ is not equivalent to <=

To use a reserved special pattern character within a Format pattern, it must be single quoted. For example, new ChoiceFormat("1#'|'foo'|'").format(1) returns "|foo|". Use two single quotes in a row to produce a literal single quote. For example, new ChoiceFormat("1# ''one'' ").format(1) returns " 'one' ".

Usage Information

A ChoiceFormat can be constructed using either an array of formats and an array of limits or a string pattern. When constructing with format and limit arrays, the length of these arrays must be the same. For example,

limits = {1,2,3,4,5,6,7}
formats = {"Sun","Mon","Tue","Wed","Thur","Fri","Sat"}
limits = {0, 1, ChoiceFormat.nextDouble(1)}
formats = {"no files", "one file", "many files"}
(nextDouble can be used to get the next higher double, to make the half-open interval.)

Below is an example of constructing a ChoiceFormat with arrays to format and parse values:

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));
}

Below is an example of constructing a ChoiceFormat with a String pattern:

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(fmt.format(Double.NEGATIVE_INFINITY)); // outputs "is negative"
System.out.println(fmt.format(-1.0)); // outputs "is negative"
System.out.println(fmt.format(0)); // outputs "is zero or fraction"
System.out.println(fmt.format(0.9)); // outputs "is zero or fraction"
System.out.println(fmt.format(1)); // outputs "is one"
System.out.println(fmt.format(1.5)); // outputs "is 1+"
System.out.println(fmt.format(2)); // outputs "is two"
System.out.println(fmt.format(2.1)); // outputs "is more than 2."
System.out.println(fmt.format(Double.NaN)); // outputs "is negative"
System.out.println(fmt.format(Double.POSITIVE_INFINITY)); // outputs "is more than 2."

For more sophisticated patterns, ChoiceFormat can be used with MessageFormat to produce accurate forms for singular and plural:

MessageFormat msgFmt = new MessageFormat("The disk \"{0}\" contains {1}.");
double[] fileLimits = {0,1,2};
String[] filePart = {"no files","one file","{1,number} files"};
ChoiceFormat fileChoices = new ChoiceFormat(fileLimits, filePart);
msgFmt.setFormatByArgumentIndex(1, fileChoices);
Object[] args = {"MyDisk", 1273};
System.out.println(msgFmt.format(args));

The output with different values for fileCount:

The disk "MyDisk" contains no files.
The disk "MyDisk" contains one file.
The disk "MyDisk" contains 1,273 files.

See MessageFormat for caveats regarding MessageFormat patterns within a ChoiceFormat pattern.

Synchronization

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.

API Note:

A subclass could perform more consistent pattern validation by throwing an IllegalArgumentException for all incorrect cases. See the Implementation Note for this implementation's behavior regarding incorrect patterns.

This class inherits instance methods from NumberFormat it does not utilize; a subclass could override and throw UnsupportedOperationException for such methods.

Implementation Note:

Given an incorrect pattern, this implementation may either throw an exception or succeed and discard the incorrect portion. A


NumberFormatException

is thrown if a limit can not be parsed as a numeric value and an IllegalArgumentException is thrown if a SubPattern is missing, or the intervals are not ascending. Discarding the incorrect portion may result in a ChoiceFormat with empty limits and formats.

Since:

1.1

See Also:

Nested Class Summary

Nested classes/interfaces declared in class NumberFormat

NumberFormat.Field, NumberFormat.Style

Modifier and Type	Class	Description
`static class`	`NumberFormat.Field`	Defines constants that are used as attribute keys in the `AttributedCharacterIterator` returned from `NumberFormat.formatToCharacterIterator` and as field identifiers in `FieldPosition`.
`static enum`	`NumberFormat.Style`	A number format style.

Field Summary

Fields declared in class NumberFormat

FRACTION_FIELD, INTEGER_FIELD

Modifier and Type	Field	Description
`static final int`	`FRACTION_FIELD`	Field constant used to construct a FieldPosition object.
`static final int`	`INTEGER_FIELD`	Field constant used to construct a FieldPosition object.

Constructor Summary

Constructor	Description
`ChoiceFormat(double[] limits, String[] formats)`	Constructs with the limits and the corresponding formats.
`ChoiceFormat(String newPattern)`	Constructs a ChoiceFormat with limits and corresponding formats based on the pattern.

Method Summary

Modifier and Type	Method	Description
`void`	`applyPattern(String newPattern)`	Apply the given pattern to this ChoiceFormat object.
`Object`	`clone()`	Overrides Cloneable
`boolean`	`equals(Object obj)`	Compares the specified object with this `ChoiceFormat` for equality.
`StringBuffer`	`format(double number, StringBuffer toAppendTo, FieldPosition status)`	Returns pattern with formatted double.
`StringBuffer`	`format(long number, StringBuffer toAppendTo, FieldPosition status)`	Specialization of format.
`Object[]`	`getFormats()`	Returns the formats of this ChoiceFormat.
`double[]`	`getLimits()`	Returns the limits of this ChoiceFormat.
`int`	`hashCode()`	Returns the hash code for this `ChoiceFormat`.
`boolean`	`isStrict()`	Returns `true` if this format will parse numbers strictly; `false` otherwise.
`static final double`	`nextDouble(double d)`	Finds the least double greater than `d`.
`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`).
`Number`	`parse(String text, ParsePosition status)`	Parses the input text starting at the index given by the `ParsePosition` as a `Double`.
`static final double`	`previousDouble(double d)`	Finds the greatest double less than `d`.
`void`	`setChoices(double[] limits, String[] formats)`	Set the choices to be used in formatting.
`void`	`setStrict(boolean strict)`	Change the leniency value for parsing.
`String`	`toPattern()`	Returns a pattern `string` that represents the `limits` and `formats` of this ChoiceFormat object.
`String`	`toString()`	Returns a string identifying this `ChoiceFormat`, for debugging.

Methods declared in class NumberFormat

format, 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

Modifier and Type	Method	Description
`final String`	`format(double number)`	Specialization of format.
`final String`	`format(long number)`	Specialization of format.
`StringBuffer`	`format(Object number, StringBuffer toAppendTo, FieldPosition pos)`	Formats a number and appends the resulting text to the given string buffer.
`static Locale[]`	`getAvailableLocales()`	Returns an array of all locales for which the `get*Instance` methods of this class can return localized instances.
`static NumberFormat`	`getCompactNumberInstance()`	Returns a compact number format for the default `FORMAT` locale with `"SHORT"` format style.
`static NumberFormat`	`getCompactNumberInstance(Locale locale, NumberFormat.Style formatStyle)`	Returns a compact number format for the specified `locale` and `formatStyle`.
`Currency`	`getCurrency()`	Gets the currency used by this number format when formatting currency values.
`static final NumberFormat`	`getCurrencyInstance()`	Returns a currency format for the current default `FORMAT` locale.
`static NumberFormat`	`getCurrencyInstance(Locale inLocale)`	Returns a currency format for the specified locale.
`static final NumberFormat`	`getInstance()`	Returns a general-purpose number format for the current default `FORMAT` locale.
`static NumberFormat`	`getInstance(Locale inLocale)`	Returns a general-purpose number format for the specified locale.
`static final NumberFormat`	`getIntegerInstance()`	Returns an integer number format for the current default `FORMAT` locale.
`static NumberFormat`	`getIntegerInstance(Locale inLocale)`	Returns an integer number format for the specified locale.
`int`	`getMaximumFractionDigits()`	Returns the maximum number of digits allowed in the fraction portion of a number during formatting.
`int`	`getMaximumIntegerDigits()`	Returns the maximum number of digits allowed in the integer portion of a number during formatting.
`int`	`getMinimumFractionDigits()`	Returns the minimum number of digits allowed in the fraction portion of a number during formatting.
`int`	`getMinimumIntegerDigits()`	Returns the minimum number of digits allowed in the integer portion of a number during formatting.
`static final NumberFormat`	`getNumberInstance()`	Returns a general-purpose number format for the current default `FORMAT` locale.
`static NumberFormat`	`getNumberInstance(Locale inLocale)`	Returns a general-purpose number format for the specified locale.
`static final NumberFormat`	`getPercentInstance()`	Returns a percentage format for the current default `FORMAT` locale.
`static NumberFormat`	`getPercentInstance(Locale inLocale)`	Returns a percentage format for the specified locale.
`RoundingMode`	`getRoundingMode()`	Gets the `RoundingMode` used in this NumberFormat.
`boolean`	`isGroupingUsed()`	Returns true if grouping is used in this format.
`boolean`	`isParseIntegerOnly()`	Returns `true` if this format will parse numbers as integers only.
`Number`	`parse(String source)`	Parses text from the beginning of the given string to produce a `Number`.
`final Object`	`parseObject(String source, ParsePosition pos)`	Parses text from the given string to produce an object.
`void`	`setCurrency(Currency currency)`	Sets the currency used by this number format when formatting currency values.
`void`	`setGroupingUsed(boolean newValue)`	Set whether or not grouping will be used in this format.
`void`	`setMaximumFractionDigits(int newValue)`	Sets the maximum number of digits allowed in the fraction portion of a number during formatting.
`void`	`setMaximumIntegerDigits(int newValue)`	Sets the maximum number of digits allowed in the integer portion of a number during formatting.
`void`	`setMinimumFractionDigits(int newValue)`	Sets the minimum number of digits allowed in the fraction portion of a number during formatting.
`void`	`setMinimumIntegerDigits(int newValue)`	Sets the minimum number of digits allowed in the integer portion of a number during formatting.
`void`	`setParseIntegerOnly(boolean value)`	Sets whether or not numbers should be parsed as integers only.
`void`	`setRoundingMode(RoundingMode roundingMode)`	Sets the `RoundingMode` used in this NumberFormat.

Methods declared in class Format

format, formatToCharacterIterator, parseObject

Modifier and Type	Method	Description
`final String`	`format(Object obj)`	Formats an object to produce a string.
`AttributedCharacterIterator`	`formatToCharacterIterator(Object obj)`	Formats an Object producing an `AttributedCharacterIterator`.
`Object`	`parseObject(String source)`	Parses text from the beginning of the given string to produce an object.

Methods declared in class Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Modifier and Type	Method	Description
`protected void`	`finalize()`	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
`final Class<?>`	`getClass()`	Returns the runtime class of this `Object`.
`final void`	`notify()`	Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()`	Wakes up all threads that are waiting on this object's monitor.
`final void`	`wait()`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
`final void`	`wait(long timeoutMillis)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis, int nanos)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Constructor Details

ChoiceFormat

public ChoiceFormat(String newPattern)

Constructs a ChoiceFormat with limits and corresponding formats based on the pattern. The syntax and error related caveats for the ChoiceFormat pattern can be found in the Patterns section. Unlike ChoiceFormat(double[], String[]), this constructor will throw an IllegalArgumentException if the limits are not in ascending order.

Parameters:

newPattern - the new pattern string

Throws:

NullPointerException - if newPattern is null

IllegalArgumentException - if newPattern violates the pattern syntax

See Also:

ChoiceFormat

public ChoiceFormat(double[] limits, String[] formats)

Constructs with the limits and the corresponding formats.

Parameters:

limits - limits in ascending order

formats - corresponding format strings

Throws:

NullPointerException - if limits or formats is null

IllegalArgumentException - if the length of limits and formats are not equal

See Also:

Method Details

applyPattern

public void applyPattern(String newPattern)

Apply the given pattern to this ChoiceFormat object. The syntax and error related caveats for the ChoiceFormat pattern can be found in the Patterns section. Unlike setChoices(double[], String[]), this method will throw an IllegalArgumentException if the limits are not in ascending order.

Parameters:

newPattern - a pattern string

Throws:

NullPointerException - if newPattern is null

IllegalArgumentException - if newPattern violates the pattern syntax

See Also:

toPattern

public String toPattern()

Returns a pattern string that represents the limits and formats of this ChoiceFormat object. The string returned is not guaranteed to be the same input string passed to either applyPattern(String) or ChoiceFormat(String).

Returns:

a pattern string that represents the limits and formats of this ChoiceFormat object

See Also:

setChoices

public void setChoices(double[] limits, String[] formats)

Set the choices to be used in formatting.

Parameters:: 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.
Throws:: NullPointerException - if limits or formats is null; IllegalArgumentException - if the length of limits and formats are not equal

getLimits

public double[] getLimits()

Returns the limits of this ChoiceFormat.

Returns:: the limits of this ChoiceFormat

getFormats

public Object[] getFormats()

Returns the formats of this ChoiceFormat.

Returns:: the formats of this ChoiceFormat

format

public StringBuffer format(long number, StringBuffer toAppendTo, FieldPosition status)

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.

Specified by:

format in class NumberFormat

Parameters:

number - number to be formatted and substituted.

toAppendTo - where text is appended.

status - ignore no useful status is returned.

Returns:

the formatted StringBuffer

Throws:

ArrayIndexOutOfBoundsException - if either the limits or formats of this ChoiceFormat are empty

NullPointerException - if toAppendTo is null

See Also:

format

public StringBuffer format(double number, StringBuffer toAppendTo, FieldPosition status)

Returns pattern with formatted double.

Specified by:

format in class NumberFormat

Parameters:

number - number to be formatted and substituted.

toAppendTo - where text is appended.

status - ignore no useful status is returned.

Returns:

the formatted StringBuffer

Throws:

ArrayIndexOutOfBoundsException - if either the limits or formats of this ChoiceFormat are empty

NullPointerException - if toAppendTo is null

See Also:

parse

public Number parse(String text, ParsePosition status)

Parses the input text starting at the index given by the ParsePosition as a Double. The value returned is the limit corresponding to the format that is the longest substring of the input text. Matching is done in ascending order, when multiple formats match the text equivalently in strength, the first matching limit is returned. If there is no match, Double.NaN is returned.

For example,

var fmt = new ChoiceFormat("0#foo|1#bar|2#baz");
fmt.parse("baz", new ParsePosition(0)); // returns 2.0
fmt.parse("quux", new ParsePosition(0)); // returns NaN

Specified by:

parse in class NumberFormat

Parameters:

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.

Returns:

A Number which represents the limit corresponding to the format parsed, or Double.NaN if the parse fails.

Throws:

NullPointerException - if status is null or if text is null and the list of choice strings is not empty.

See Also:

isStrict

public boolean isStrict()

Description copied from class: NumberFormat

Returns true if this format will parse numbers strictly; false otherwise.

Overrides:

isStrict in class NumberFormat

Returns:

true if this format will parse numbers strictly; false otherwise

Since:

See Also:

setStrict

public void setStrict(boolean strict)

Description copied from class: NumberFormat

Change the leniency value for parsing. Parsing can either be strict or lenient, by default it is lenient.

Overrides:

setStrict in class NumberFormat

Parameters:

strict - true if parsing should be done strictly; false otherwise

Since:

See Also:

nextDouble

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.

Implementation Note:

This is equivalent to calling Math.nextUp(d)

Parameters:

d - the reference value

Returns:

the least double value greater than d

See Also:

nextDouble

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.

Implementation Note:: This is equivalent to calling positive ? Math.nextUp(d) : Math.nextDown(d)
Parameters:: d - the reference value; positive - true if the least double is desired; false otherwise
Returns:: the least or greater double value

previousDouble

public static final double previousDouble(double d)

Finds the greatest double less than d. If NaN, returns same value.

Implementation Note:

This is equivalent to calling Math.nextDown(d)

Parameters:

d - the reference value

Returns:

the greatest double value less than d

See Also:

clone

public Object clone()

Overrides Cloneable

Overrides:

clone in class NumberFormat

Returns:

a clone of this instance.

See Also:

hashCode

public int hashCode()

Returns the hash code for this ChoiceFormat.

Overrides:

hashCode in class NumberFormat

Implementation Requirements:

This method calculates the hash code value using the values returned by getFormats() and getLimits().

Returns:

the hash code for this ChoiceFormat

See Also:

toString

public String toString()

Returns a string identifying this ChoiceFormat, for debugging.

Overrides:: toString in class Object
Returns:: a string identifying this ChoiceFormat, for debugging

equals

public boolean equals(Object obj)

Compares the specified object with this ChoiceFormat for equality. Returns true if the object is also a ChoiceFormat and the two formats would format any value the same.

Overrides:

equals in class NumberFormat

Implementation Requirements:

This method performs an equality check with a notion of class identity based on getClass(), rather than instanceof. Therefore, in the equals methods in subclasses, no instance of this class should compare as equal to an instance of a subclass.

Parameters:

obj - object to be compared for equality

Returns:

true if the specified object is equal to this ChoiceFormat

See Also:

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