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ChoiceFormat

public class ChoiceFormat
extends NumberFormat

java.lang.Object
   ↳ java.text.Format
     ↳ java.text.NumberFormat
       ↳ java.text.ChoiceFormat


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,

  • 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.)

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:
   Format 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.
 

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.

See also:

Summary

Inherited constants

From class java.text.NumberFormat

Public constructors

ChoiceFormat(String newPattern)

Constructs with limits and corresponding formats based on the pattern.

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

Constructs with the limits and the corresponding formats.

Public methods

void applyPattern(String newPattern)

Sets the pattern.

Object clone()

Overrides Cloneable

boolean equals(Object obj)

Equality comparision between two

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()

Get the formats passed in the constructor.

double[] getLimits()

Get the limits passed in the constructor.

int hashCode()

Generates a hash code for the message format object.

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 == true), or the greatest double less than d (if positive == false).

Number parse(String text, ParsePosition status)

Parses a Number from the input text.

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.

String toPattern()

Gets the pattern.

Inherited methods

From class java.text.NumberFormat
From class java.text.Format
From class java.lang.Object

Public constructors

ChoiceFormat

Added in API level 1
ChoiceFormat (String newPattern)

Constructs with limits and corresponding formats based on the pattern.

Parameters
newPattern String

See also:

ChoiceFormat

Added in API level 1
ChoiceFormat (double[] limits, 
                String[] formats)

Constructs with the limits and the corresponding formats.

Parameters
limits double
formats String

See also:

Public methods

applyPattern

Added in API level 1
void applyPattern (String newPattern)

Sets the pattern.

Parameters
newPattern String: See the class description.

clone

Added in API level 1
Object clone ()

Overrides Cloneable

Returns
Object a clone of this instance.

equals

Added in API level 1
boolean equals (Object obj)

Equality comparision between two

Parameters
obj Object: the reference object with which to compare.
Returns
boolean true if this object is the same as the obj argument; false otherwise.

format

Added in API level 1
StringBuffer format (double number, 
                StringBuffer toAppendTo, 
                FieldPosition status)

Returns pattern with formatted double.

Parameters
number double: number to be formatted & substituted.
toAppendTo StringBuffer: where text is appended.
status FieldPosition: ignore no useful status is returned.
Returns
StringBuffer

format

Added in API level 1
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.

Parameters
number long
toAppendTo StringBuffer
status FieldPosition
Returns
StringBuffer

getFormats

Added in API level 1
Object[] getFormats ()

Get the formats passed in the constructor.

Returns
Object[] the formats.

getLimits

Added in API level 1
double[] getLimits ()

Get the limits passed in the constructor.

Returns
double[] the limits.

hashCode

Added in API level 1
int hashCode ()

Generates a hash code for the message format object.

Returns
int a hash code value for this object.

nextDouble

Added in API level 1
double nextDouble (double d)

Finds the least double greater than d. If NaN, returns same value.

Used to make half-open intervals.

Parameters
d double
Returns
double

See also:

nextDouble

Added in API level 1
double nextDouble (double d, 
                boolean positive)

Finds the least double greater than d (if positive == true), or the greatest double less than d (if positive == false). If NaN, returns same value. Does not affect floating-point flags, provided these member functions do not: Double.longBitsToDouble(long) Double.doubleToLongBits(double) Double.isNaN(double)

Parameters
d double
positive boolean
Returns
double

parse

Added in API level 1
Number parse (String text, 
                ParsePosition status)

Parses a Number from the input text.

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 occured, 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 representing the value of the number parsed.

previousDouble

Added in API level 1
double previousDouble (double d)

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

Parameters
d double
Returns
double

See also:

setChoices

Added in API level 1
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. 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.

toPattern

Added in API level 1
String toPattern ()

Gets the pattern.

Returns
String
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