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java.text

public Class ChoiceFormat

extends NumberFormat
Class Inheritance
Imports
java.io.InvalidObjectException, .IOException, .ObjectInputStream, java.util.ArrayList, .Arrays, .Objects
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,

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)); } 
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." 
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)); 
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.

Author
Mark Davis
Since
1.1
See Also
DecimalFormat, MessageFormat

Field Summary

Modifier and TypeField and Description
private String[]
choiceFormats

A list of choice strings.

private double[]
choiceLimits

A list of lower bounds for the choices.

private static final long
serialVersionUID

Hides java.text.NumberFormat.serialVersionUID.

Inherited from java.text.NumberFormat:
currentSerialVersionFRACTION_FIELDINTEGER_FIELD

Constructor Summary

AccessConstructor and Description
public
ChoiceFormat(String
the new pattern string
newPattern)

Constructs a ChoiceFormat with limits and corresponding formats based on the pattern.

public
ChoiceFormat(double[]
limits in ascending order
limits, String[]
corresponding format strings
formats)

Constructs with the limits and the corresponding formats.

Method Summary

Modifier and TypeMethod and Description
public void
applyPattern(String
a pattern string
newPattern)

Apply the given pattern to this ChoiceFormat object.

private void
applyPatternImpl(String newPattern)

Implementation of applying a pattern to this ChoiceFormat.

public Object
clone()

Overrides java.text.NumberFormat.clone.

Overrides Cloneable

public boolean

Returns:

true if the specified object is equal to this ChoiceFormat
equals(Object
object to be compared for equality
obj)

Overrides java.text.NumberFormat.equals.

Compares the specified object with this ChoiceFormat for equality.

public StringBuffer
format(long
number to be formatted and substituted.
number, StringBuffer
where text is appended.
toAppendTo, FieldPosition
ignore no useful status is returned.
status)

Implements abstract java.text.NumberFormat.format.

Specialization of format.

pack-priv Format.StringBuf
format(long number, Format.StringBuf toAppendTo, FieldPosition status)

Overrides java.text.NumberFormat.format.

public StringBuffer
format(double
number to be formatted and substituted.
number, StringBuffer
where text is appended.
toAppendTo, FieldPosition
ignore no useful status is returned.
status)

Implements abstract java.text.NumberFormat.format.

Returns pattern with formatted double.

pack-priv Format.StringBuf
format(double number, Format.StringBuf toAppendTo, FieldPosition status)

Overrides java.text.NumberFormat.format.

public Object[]

Returns:

the formats of this ChoiceFormat
getFormats()

Returns the formats of this ChoiceFormat.

public double[]

Returns:

the limits of this ChoiceFormat
getLimits()

Returns the limits of this ChoiceFormat.

public int

Returns:

the hash code for this ChoiceFormat
hashCode()

Overrides java.text.NumberFormat.hashCode.

Returns the hash code for this ChoiceFormat.

public boolean
isStrict()

Overrides java.text.NumberFormat.isStrict.

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

public static final double

Returns:

the least double value greater than d
nextDouble(double
the reference value
d)

Finds the least double greater than d.

public static double

Returns:

the least or greater double value
nextDouble(double
the reference value
d, boolean
true if the least double is desired; false otherwise
positive)

Finds the least double greater than d (if positive is true), or the greatest double less than d (if positive is false).

public Number

Returns:

A Number which represents the limit corresponding to the format parsed, or Double.NaN if the parse fails.
parse(String
the source text.
text, ParsePosition
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.
status)

Implements abstract java.text.NumberFormat.parse.

Parses the input text starting at the index given by the ParsePosition as a Double.

public static final double

Returns:

the greatest double value less than d
previousDouble(double
the reference value
d)

Finds the greatest double less than d.

private void
readObject(ObjectInputStream in)

Hides java.text.NumberFormat.readObject.

After reading an object from the input stream, do a simple verification to maintain class invariants.

public void
setChoices(double[]
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.
limits, String[]
are the formats you want to use for each limit.
formats)

Set the choices to be used in formatting.

private void
setChoicesImpl(double[] limits, String[] formats)

Implementation of populating the limits and formats of this ChoiceFormat.

public void
setStrict(boolean strict)

Overrides java.text.NumberFormat.setStrict.

Change the leniency value for parsing.

private static double
stringToNum(String str)

Converts a string value to its double representation; this is used to create the limit segment while applying a pattern.

public String

Returns:

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

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

public String

Returns:

a string identifying this ChoiceFormat, for debugging
toString()

Overrides java.lang.Object.toString.

Returns a string identifying this ChoiceFormat, for debugging.

Inherited from java.text.NumberFormat:
fastFormatformatformatformatformatgetAvailableLocalesgetCompactNumberInstancegetCompactNumberInstancegetCurrencygetCurrencyInstancegetCurrencyInstancegetInstancegetInstancegetIntegerInstancegetIntegerInstancegetMaximumFractionDigitsgetMaximumIntegerDigitsgetMinimumFractionDigitsgetMinimumIntegerDigitsgetNumberInstancegetNumberInstancegetPercentInstancegetPercentInstancegetRoundingModegetScientificInstancegetScientificInstanceisGroupingUsedisParseIntegerOnlymatchToStyleparseparseObjectsetCurrencysetGroupingUsedsetMaximumFractionDigitssetMaximumIntegerDigitssetMinimumFractionDigitssetMinimumIntegerDigitssetParseIntegerOnlysetRoundingMode

Field Detail

choiceFormatsback to summary
private String[] choiceFormats

A list of choice strings. The formatter will return choiceFormats[i] if the number being formatted is greater than or equal to choiceLimits[i] and less than choiceLimits[i+1].

choiceLimitsback to summary
private double[] choiceLimits

A list of lower bounds for the choices. The formatter will return choiceFormats[i] if the number being formatted is greater than or equal to choiceLimits[i] and less than choiceLimits[i+1].

serialVersionUIDback to summary
private static final long serialVersionUID

Hides java.text.NumberFormat.serialVersionUID.

Annotations
@Serial

Constructor Detail

ChoiceFormatback to summary
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:String

the new pattern string

Exceptions
NullPointerException:
if newPattern is null
IllegalArgumentException:
if newPattern violates the pattern syntax
See Also
applyPattern
ChoiceFormatback to summary
public ChoiceFormat(double[] limits, String[] formats)

Constructs with the limits and the corresponding formats.

Parameters
limits:double[]

limits in ascending order

formats:String[]

corresponding format strings

Exceptions
NullPointerException:
if limits or formats is null
IllegalArgumentException:
if the length of limits and formats are not equal
See Also
setChoices

Method Detail

applyPatternback to summary
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:String

a pattern string

Exceptions
NullPointerException:
if newPattern is null
IllegalArgumentException:
if newPattern violates the pattern syntax
See Also
ChoiceFormat(String)
applyPatternImplback to summary
private void applyPatternImpl(String newPattern)

Implementation of applying a pattern to this ChoiceFormat. This method processes a String pattern in accordance with the ChoiceFormat pattern syntax and populates the internal limits and formats array variables. See the patterns section for further understanding of certain special characters: "#", "<", "≤", "|".

cloneback to summary
public Object clone()

Overrides java.text.NumberFormat.clone.

Overrides Cloneable

Annotations
@Override
equalsback to summary
public boolean equals(Object obj)

Overrides java.text.NumberFormat.equals.

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.

Implementation Specification

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

object to be compared for equality

Returns:boolean

true if the specified object is equal to this ChoiceFormat

Annotations
@Override
See Also
Object#equals(Object)
formatback to summary
public StringBuffer format(long number, StringBuffer toAppendTo, FieldPosition status)

Implements abstract java.text.NumberFormat.format.

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.

Parameters
number:long

number to be formatted and substituted.

toAppendTo:StringBuffer

where text is appended.

status:FieldPosition

ignore no useful status is returned.

Annotations
@Override
Exceptions
ArrayIndexOutOfBoundsException:
if either the limits or formats of this ChoiceFormat are empty
NullPointerException:
if toAppendTo is null
formatback to summary
pack-priv Format.StringBuf format(long number, Format.StringBuf toAppendTo, FieldPosition status)

Overrides java.text.NumberFormat.format.

Annotations
@Override
formatback to summary
public StringBuffer format(double number, StringBuffer toAppendTo, FieldPosition status)

Implements abstract java.text.NumberFormat.format.

Returns pattern with formatted double.

Parameters
number:double

number to be formatted and substituted.

toAppendTo:StringBuffer

where text is appended.

status:FieldPosition

ignore no useful status is returned.

Annotations
@Override
Exceptions
ArrayIndexOutOfBoundsException:
if either the limits or formats of this ChoiceFormat are empty
NullPointerException:
if toAppendTo is null
formatback to summary
pack-priv Format.StringBuf format(double number, Format.StringBuf toAppendTo, FieldPosition status)

Overrides java.text.NumberFormat.format.

Annotations
@Override
getFormatsback to summary
public Object[] getFormats()

Returns the formats of this ChoiceFormat.

Returns:Object[]

the formats of this ChoiceFormat

getLimitsback to summary
public double[] getLimits()

Returns the limits of this ChoiceFormat.

Returns:double[]

the limits of this ChoiceFormat

hashCodeback to summary
public int hashCode()

Overrides java.text.NumberFormat.hashCode.

Returns the hash code for this ChoiceFormat.

Implementation Specification

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

Returns:int

the hash code for this ChoiceFormat

Annotations
@Override
See Also
Object#hashCode()
isStrictback to summary
public boolean isStrict()

Overrides java.text.NumberFormat.isStrict.

Doc from java.text.NumberFormat.isStrict.

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

Annotations
@Override
Since
23
nextDoubleback to summary
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:double

the reference value

Returns:double

the least double value greater than d

See Also
previousDouble
nextDoubleback to summary
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:double

the reference value

positive:boolean

true if the least double is desired; false otherwise

Returns:double

the least or greater double value

parseback to summary
public Number parse(String text, ParsePosition status)

Implements abstract java.text.NumberFormat.parse.

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 
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
Parameters
text:String

the source text.

status:ParsePosition

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:Number

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

Annotations
@Override
Exceptions
NullPointerException:
if status is null or if text is null and the list of choice strings is not empty.
previousDoubleback to summary
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:double

the reference value

Returns:double

the greatest double value less than d

See Also
nextDouble
readObjectback to summary
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException

Hides java.text.NumberFormat.readObject.

After reading an object from the input stream, do a simple verification to maintain class invariants.

Annotations
@Serial
Exceptions
InvalidObjectException:
if the objects read from the stream is invalid.
setChoicesback to summary
public void setChoices(double[] limits, String[] formats)

Set the choices to be used in formatting.

Parameters
limits:double[]

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:String[]

are the formats you want to use for each limit.

Exceptions
NullPointerException:
if limits or formats is null
IllegalArgumentException:
if the length of limits and formats are not equal
setChoicesImplback to summary
private void setChoicesImpl(double[] limits, String[] formats)

Implementation of populating the limits and formats of this ChoiceFormat. Defensive copies are made.

setStrictback to summary
public void setStrict(boolean strict)

Overrides java.text.NumberFormat.setStrict.

Doc from java.text.NumberFormat.setStrict.

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

Annotations
@Override
Since
23
stringToNumback to summary
private static double stringToNum(String str)

Converts a string value to its double representation; this is used to create the limit segment while applying a pattern. Handles "∞", as specified by the pattern syntax.

toPatternback to summary
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:String

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

See Also
applyPattern(String)
toStringback to summary
public String toString()

Overrides java.lang.Object.toString.

Returns a string identifying this ChoiceFormat, for debugging.

Returns:String

a string identifying this ChoiceFormat, for debugging

Annotations
@Override