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,
-
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:
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.
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
Inherited Constant Summary
Public Constructor Summary
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 Method Summary
void | |
Object |
clone()
Overrides Cloneable
|
boolean | |
StringBuffer |
format(double number, StringBuffer toAppendTo, FieldPosition status)
Returns pattern with formatted double.
|
StringBuffer | |
Object[] | |
double[] | |
int |
hashCode()
Generates a hash code for the message format object.
|
final static 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 | |
final static double |
previousDouble(double d)
Finds the greatest double less than
d . |
void | |
String |
toPattern()
Gets the pattern.
|
Inherited Method Summary
Public Constructors
public ChoiceFormat (String newPattern)
Constructs with limits and corresponding formats based on the pattern.
Parameters
newPattern | the new pattern string |
---|
See Also
public ChoiceFormat (double[] limits, String[] formats)
Constructs with the limits and the corresponding formats.
Parameters
limits | limits in ascending order |
---|---|
formats | corresponding format strings |
See Also
Public Methods
public void applyPattern (String newPattern)
Sets the pattern.
Parameters
newPattern | See the class description. |
---|
public boolean equals (Object obj)
Equality comparision between two
Parameters
obj | the object to compare this instance with. |
---|
Returns
true
if the specified object is equal to thisObject
;false
otherwise.
public StringBuffer format (double number, StringBuffer toAppendTo, FieldPosition status)
Returns pattern with formatted double.
Parameters
number | number to be formatted and substituted. |
---|---|
toAppendTo | where text is appended. |
status | ignore no useful status is returned. |
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.
Parameters
number | |
---|---|
toAppendTo | |
status |
public Object[] getFormats ()
Returns
- a copy of the
String[]
array supplied to the constructor or the most recent call tosetChoices(double[], String[])
.
public double[] getLimits ()
Returns
- a copy of the
double[]
array supplied to the constructor or the most recent call tosetChoices(double[], String[])
.
public int hashCode ()
Generates a hash code for the message format object.
Returns
- this object's hash code.
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.
Parameters
d | the reference value |
---|
Returns
- the least double value greather than
d
See Also
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.
Does not affect floating-point flags,
provided these member functions do not:
Double.longBitsToDouble(long)
Double.doubleToLongBits(double)
Double.isNaN(double)
Parameters
d | the reference value |
---|---|
positive | true if the least double is desired;
false otherwise |
Returns
- the least or greater double value
public Number parse (String text, ParsePosition status)
Parses a Number from the input text.
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 representing the value of the number parsed.
public static final double previousDouble (double d)
Finds the greatest double less than d
.
If NaN
, returns same value.
Parameters
d | the reference value |
---|
Returns
- the greatest double value less than
d
See Also
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. 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. |