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:
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:
Summary
Inherited constants |
---|
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 comparison 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()
|
double[]
|
getLimits()
|
int
|
hashCode()
Generates a hash code for the message format object. |
static
final
double
|
nextDouble(double d)
Finds the least double greater than |
static
double
|
nextDouble(double d, boolean positive)
Finds the least double greater than |
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 |
void
|
setChoices(double[] limits, String[] formats)
Set the choices to be used in formatting. |
String
|
toPattern()
Gets the pattern. |
Inherited methods | |
---|---|
Public constructors
ChoiceFormat
public ChoiceFormat (String newPattern)
Constructs with limits and corresponding formats based on the pattern.
Parameters | |
---|---|
newPattern |
String : the new pattern string |
Throws | |
---|---|
NullPointerException |
if newPattern is
null |
See also:
ChoiceFormat
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 |
Throws | |
---|---|
NullPointerException |
if limits or formats
is null |
See also:
Public methods
applyPattern
public void applyPattern (String newPattern)
Sets the pattern.
Parameters | |
---|---|
newPattern |
String : See the class description. |
Throws | |
---|---|
NullPointerException |
if newPattern
is null |
clone
public Object clone ()
Overrides Cloneable
Returns | |
---|---|
Object |
a clone of this instance. |
equals
public boolean equals (Object obj)
Equality comparison 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
public StringBuffer format (double number, StringBuffer toAppendTo, FieldPosition status)
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. |
Returns | |
---|---|
StringBuffer |
the formatted StringBuffer |
Throws | |
---|---|
NullPointerException |
if toAppendTo
is null |
format
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 |
long : the long number to format |
toAppendTo |
StringBuffer : the StringBuffer to which the formatted text is to be
appended |
status |
FieldPosition : keeps track on the position of the field within the
returned string. For example, for formatting a number
123456789 in Locale.US locale,
if the given fieldPosition is
NumberFormat#INTEGER_FIELD , the begin index
and end index of fieldPosition will be set
to 0 and 11, respectively for the output string
123,456,789 . |
Returns | |
---|---|
StringBuffer |
the formatted StringBuffer |
getFormats
public Object[] getFormats ()
Returns | |
---|---|
Object[] |
a copy of the String[] array supplied to the constructor or the most recent
call to setChoices(double[], java.lang.String[]) . |
getLimits
public double[] getLimits ()
Returns | |
---|---|
double[] |
a copy of the double[] array supplied to the constructor or the most recent
call to setChoices(double[], java.lang.String[]) . |
hashCode
public int hashCode ()
Generates a hash code for the message format object.
Returns | |
---|---|
int |
a hash code value for this object. |
nextDouble
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 greather than d |
See also:
nextDouble
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 |
parse
public 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
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 representing the value of the number parsed. |
Throws | |
---|---|
NullPointerException |
if status is null
or if text is null and the list of
choice strings is not empty. |
previousDouble
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:
setChoices
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.
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. |
Throws | |
---|---|
NullPointerException |
if limits or
formats is null |
toPattern
public String toPattern ()
Gets the pattern.
Returns | |
---|---|
String |
the pattern string |