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public class: ChoiceFormat [javadoc | source]

All Implemented Interfaces:
    Cloneable, Serializable

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,

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) {
    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}");
Object[] testArgs = {null, "ADisk", null};
for (int i = 0; i < 4; ++i) {
    testArgs[0] = new Integer(i);
    testArgs[2] = testArgs[0];

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.


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.

Field Summary
static final  long SIGN     
static final  long EXPONENT     
static final  long POSITIVEINFINITY     
Fields inherited from java.text.NumberFormat:
INTEGER_FIELD,  FRACTION_FIELD,  currentSerialVersion,  serialVersionUID
 public ChoiceFormat(String newPattern) 
    Constructs with limits and corresponding formats based on the pattern.
 public ChoiceFormat(double[] limits,
    String[] formats) 
    Constructs with the limits and the corresponding formats.
Method from java.text.ChoiceFormat Summary:
applyPattern,   clone,   equals,   format,   format,   getFormats,   getLimits,   hashCode,   nextDouble,   nextDouble,   parse,   previousDouble,   setChoices,   toPattern
Methods from java.text.NumberFormat:
clone,   equals,   format,   format,   format,   format,   format,   getAvailableLocales,   getCurrency,   getCurrencyInstance,   getCurrencyInstance,   getInstance,   getInstance,   getIntegerInstance,   getIntegerInstance,   getMaximumFractionDigits,   getMaximumIntegerDigits,   getMinimumFractionDigits,   getMinimumIntegerDigits,   getNumberInstance,   getNumberInstance,   getPercentInstance,   getPercentInstance,   getRoundingMode,   getScientificInstance,   getScientificInstance,   hashCode,   isGroupingUsed,   isParseIntegerOnly,   parse,   parse,   parseObject,   setCurrency,   setGroupingUsed,   setMaximumFractionDigits,   setMaximumIntegerDigits,   setMinimumFractionDigits,   setMinimumIntegerDigits,   setParseIntegerOnly,   setRoundingMode
Methods from java.text.Format:
clone,   createAttributedCharacterIterator,   createAttributedCharacterIterator,   createAttributedCharacterIterator,   createAttributedCharacterIterator,   format,   format,   formatToCharacterIterator,   parseObject,   parseObject
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from java.text.ChoiceFormat Detail:
 public  void applyPattern(String newPattern) 
    Sets the pattern.
 public Object clone() 
    Overrides Cloneable
 public boolean equals(Object obj) 
    Equality comparision between two
 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.
 public StringBuffer format(double number,
    StringBuffer toAppendTo,
    FieldPosition status) 
    Returns pattern with formatted double.
 public Object[] getFormats() 
    Get the formats passed in the constructor.
 public double[] getLimits() 
    Get the limits passed in the constructor.
 public int hashCode() 
    Generates a hash code for the message format object.
 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.

 public 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). 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)
 public Number parse(String text,
    ParsePosition status) 
    Parses a Number from the input text.
 public static final double previousDouble(double d) 
    Finds the greatest double less than d. If NaN, returns same value.
 public  void setChoices(double[] limits,
    String[] formats) 
    Set the choices to be used in formatting.
 public String toPattern() 
    Gets the pattern.