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:
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 acceptsX matches j if and only if limit[j] <= X < limit[j+1]
\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:
Here is a more complex example, with a pattern format: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[] 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:
And the output result would be like the following: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));
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.
See also:
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
|
ChoiceFormat (String newPattern)
Constructs with limits and corresponding formats based on the pattern.
Parameters | |
---|---|
newPattern |
String
|
See also:
ChoiceFormat (double[] limits, String[] formats)
Constructs with the limits and the corresponding formats.
Parameters | |
---|---|
limits |
double
|
formats |
String
|
See also:
void applyPattern (String newPattern)
Sets the pattern.
Parameters | |
---|---|
newPattern |
String :
See the class description.
|
Object clone ()
Overrides Cloneable
Returns | |
---|---|
Object |
a clone of this instance. |
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. |
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 |
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 |
Object[] getFormats ()
Get the formats passed in the constructor.
Returns | |
---|---|
Object[] |
the formats. |
double[] getLimits ()
Get the limits passed in the constructor.
Returns | |
---|---|
double[] |
the limits. |
int hashCode ()
Generates a hash code for the message format object.
Returns | |
---|---|
int |
a hash code value for this object. |
double nextDouble (double d)
Finds the least double greater than d. If NaN, returns same value.
Used to make half-open intervals.
Parameters | |
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d |
double
|
Returns | |
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double |
See also:
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 | |
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d |
double
|
positive |
boolean
|
Returns | |
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double |
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. |
double previousDouble (double d)
Finds the greatest double less than d. If NaN, returns same value.
Parameters | |
---|---|
d |
double
|
Returns | |
---|---|
double |
See also:
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.
|