com.ibm.icu.text
public class MessageFormat extends UFormat
MessageFormat
provides a means to produce concatenated
messages in language-neutral way. Use this to construct messages
displayed for end users.
MessageFormat
takes a set of objects, formats them, then
inserts the formatted strings into the pattern at the appropriate places.
Note:
MessageFormat
differs from the other Format
classes in that you create a MessageFormat
object with one
of its constructors (not with a getInstance
style factory
method). The factory methods aren't necessary because MessageFormat
itself doesn't implement locale specific behavior. Any locale specific
behavior is defined by the pattern that you provide as well as the
subformats used for inserted arguments.
MessageFormat
uses patterns of the following form:
MessageFormatPattern: String MessageFormatPattern FormatElement String FormatElement: { ArgumentIndex } { ArgumentIndex , FormatType } { ArgumentIndex , FormatType , FormatStyle } FormatType: one of number date time choice FormatStyle: short medium long full integer currency percent SubformatPattern String: StringPartopt String StringPart StringPart: '' ' QuotedString ' UnquotedString SubformatPattern: SubformatPatternPartopt SubformatPattern SubformatPatternPart SubFormatPatternPart: ' QuotedPattern ' UnquotedPattern
Within a String, "''"
represents a single
quote. A QuotedString can contain arbitrary characters
except single quotes; the surrounding single quotes are removed.
An UnquotedString can contain arbitrary characters
except single quotes and left curly brackets. Thus, a string that
should result in the formatted message "'{0}'" can be written as
"'''{'0}''"
or "'''{0}'''"
.
Within a SubformatPattern, different rules apply.
A QuotedPattern can contain arbitrary characters
except single quotes; but the surrounding single quotes are
not removed, so they may be interpreted by the
subformat. For example, "{1,number,$'#',##}"
will
produce a number format with the pound-sign quoted, with a result
such as: "$#31,45".
An UnquotedPattern can contain arbitrary characters
except single quotes, but curly braces within it must be balanced.
For example, "ab {0} de"
and "ab '}' de"
are valid subformat patterns, but "ab {0'}' de"
and
"ab } de"
are not.
The ArgumentIndex value is a non-negative integer written
using the digits '0' through '9', and represents an index into the
arguments
array passed to the format
methods
or the result array returned by the parse
methods.
The FormatType and FormatStyle values are used to create
a Format
instance for the format element. The following
table shows how the values map to Format instances. Combinations not
shown in the table are illegal. A SubformatPattern must
be a valid pattern string for the Format subclass used.
Format Type | Format Style | Subformat Created | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
(none) | null
| ||||||||||||||||
number
| (none) | NumberFormat.getInstance(getLocale())
| |||||||||||||||
integer
| NumberFormat.getIntegerInstance(getLocale())
| ||||||||||||||||
currency
| NumberFormat.getCurrencyInstance(getLocale())
| ||||||||||||||||
percent
| NumberFormat.getPercentInstance(getLocale())
| ||||||||||||||||
SubformatPattern | new DecimalFormat(subformatPattern, new DecimalFormatSymbols(getLocale()))
| ||||||||||||||||
date
| (none) | DateFormat.getDateInstance(DateFormat.DEFAULT, getLocale())
| |||||||||||||||
short
| DateFormat.getDateInstance(DateFormat.SHORT, getLocale())
| ||||||||||||||||
medium
| DateFormat.getDateInstance(DateFormat.DEFAULT, getLocale())
| ||||||||||||||||
long
| DateFormat.getDateInstance(DateFormat.LONG, getLocale())
| ||||||||||||||||
full
| DateFormat.getDateInstance(DateFormat.FULL, getLocale())
| ||||||||||||||||
SubformatPattern | new SimpleDateFormat(subformatPattern, getLocale())
|
Here are some examples of usage:
Typically, the message format will come from resources, and the arguments will be dynamically set at runtime.Object[] arguments = { new Integer(7), new Date(System.currentTimeMillis()), "a disturbance in the Force" }; String result = MessageFormat.format( "At {1,time} on {1,date}, there was {2} on planet {0,number,integer}.", arguments); output: At 12:30 PM on Jul 3, 2053, there was a disturbance in the Force on planet 7.
Example 2:
Object[] testArgs = {new Long(3), "MyDisk"}; MessageFormat form = new MessageFormat( "The disk \"{1}\" contains {0} file(s)."); System.out.println(form.format(testArgs)); // output, with different testArgs output: The disk "MyDisk" contains 0 file(s). output: The disk "MyDisk" contains 1 file(s). output: The disk "MyDisk" contains 1,273 file(s).
For more sophisticated patterns, you can use a ChoiceFormat
to get
output such as:
You can either do this programmatically, as in the above example, or by using a pattern (see ChoiceFormat for more information) as in:MessageFormat form = new MessageFormat("The disk \"{1}\" contains {0}."); double[] filelimits = {0,1,2}; String[] filepart = {"no files","one file","{0,number} files"}; ChoiceFormat fileform = new ChoiceFormat(filelimits, filepart); form.setFormatByArgumentIndex(0, fileform); Object[] testArgs = {new Long(12373), "MyDisk"}; System.out.println(form.format(testArgs)); // output, with different testArgs output: The disk "MyDisk" contains no files. output: The disk "MyDisk" contains one file. output: The disk "MyDisk" contains 1,273 files.
form.applyPattern( "There {0,choice,0#are no files|1#is one file|1<are {0,number,integer} files}.");
Note: As we see above, the string produced
by a ChoiceFormat
in MessageFormat
is treated specially;
occurances of '{' are used to indicated subformats, and cause recursion.
If you create both a MessageFormat
and ChoiceFormat
programmatically (instead of using the string patterns), then be careful not to
produce a format that recurses on itself, which will cause an infinite loop.
When a single argument is parsed more than once in the string, the last match will be the final result of the parsing. For example,
MessageFormat mf = new MessageFormat("{0,number,#.##}, {0,number,#.#}"); Object[] objs = {new Double(3.1415)}; String result = mf.format( objs ); // result now equals "3.14, 3.1" objs = null; objs = mf.parse(result, new ParsePosition(0)); // objs now equals {new Double(3.1)}
Likewise, parsing with a MessageFormat object using patterns containing multiple occurances of the same argument would return the last match. For example,
MessageFormat mf = new MessageFormat("{0}, {0}, {0}"); String forParsing = "x, y, z"; Object[] objs = mf.parse(forParsing, new ParsePosition(0)); // result now equals {new String("z")}
Message 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: java.util.Locale Format NumberFormat DecimalFormat ChoiceFormat
UNKNOWN: ICU 3.0
Constructor Summary | |
---|---|
MessageFormat(String pattern)
Constructs a MessageFormat for the default locale and the
specified pattern.
| |
MessageFormat(String pattern, Locale locale)
Constructs a MessageFormat for the specified locale and
pattern.
| |
MessageFormat(String pattern, ULocale locale)
Constructs a MessageFormat for the specified locale and
pattern.
|
Method Summary | |
---|---|
void | applyPattern(String pattern)
Sets the pattern used by this message format.
|
static String | autoQuoteApostrophe(String pattern)
Convert an 'apostrophe-friendly' pattern into a standard
pattern. |
Object | clone()
Creates and returns a copy of this object.
|
boolean | equals(Object obj)
Equality comparison between two message format objects |
StringBuffer | format(Object[] arguments, StringBuffer result, FieldPosition pos)
Formats an array of objects and appends the MessageFormat 's
pattern, with format elements replaced by the formatted objects, to the
provided StringBuffer .
|
static String | format(String pattern, Object[] arguments)
Creates a MessageFormat with the given pattern and uses it
to format the given arguments. |
StringBuffer | format(Object arguments, StringBuffer result, FieldPosition pos)
Formats an array of objects and appends the MessageFormat 's
pattern, with format elements replaced by the formatted objects, to the
provided StringBuffer .
|
Format[] | getFormats()
Gets the formats used for the format elements in the
previously set pattern string.
|
Format[] | getFormatsByArgumentIndex()
Gets the formats used for the values passed into
format methods or returned from parse
methods. |
Locale | getLocale()
Gets the locale that's used when creating or comparing subformats.
|
ULocale | getULocale()
Gets the locale that's used when creating or comparing subformats.
|
int | hashCode()
Generates a hash code for the message format object. |
Object[] | parse(String source, ParsePosition pos)
Parses the string.
|
Object[] | parse(String source)
Parses text from the beginning of the given string to produce an object
array.
|
Object | parseObject(String source, ParsePosition pos)
Parses text from a string to produce an object array.
|
void | setFormat(int formatElementIndex, Format newFormat)
Sets the format to use for the format element with the given
format element index within the previously set pattern string.
|
void | setFormatByArgumentIndex(int argumentIndex, Format newFormat)
Sets the format to use for the format elements within the
previously set pattern string that use the given argument
index.
|
void | setFormats(Format[] newFormats)
Sets the formats to use for the format elements in the
previously set pattern string.
|
void | setFormatsByArgumentIndex(Format[] newFormats)
Sets the formats to use for the values passed into
format methods or returned from parse
methods. |
void | setLocale(Locale locale)
Sets the locale to be used when creating or comparing subformats.
|
void | setLocale(ULocale locale)
Sets the locale to be used when creating or comparing subformats.
|
String | toPattern()
Returns a pattern representing the current state of the message format.
|
Parameters: pattern the pattern for this message format
Throws: IllegalArgumentException if the pattern is invalid
UNKNOWN: ICU 3.0
Parameters: pattern the pattern for this message format locale the locale for this message format
Throws: IllegalArgumentException if the pattern is invalid
UNKNOWN: ICU 3.0
Parameters: pattern the pattern for this message format locale the locale for this message format
Throws: IllegalArgumentException if the pattern is invalid
UNKNOWN: ICU 3.2
Parameters: pattern the pattern for this message format
Throws: IllegalArgumentException if the pattern is invalid
UNKNOWN: ICU 3.0
Note it is not guaranteed that the returned pattern is indeed a valid pattern. The only effect is to convert between patterns having different quoting semantics.
Parameters: pattern the 'apostrophe-friendly' patttern to convert
Returns: the standard equivalent of the original pattern
UNKNOWN: ICU 3.4 This API might change or be removed in a future release.
Returns: a clone of this instance.
UNKNOWN: ICU 3.0
UNKNOWN: ICU 3.0
MessageFormat
's
pattern, with format elements replaced by the formatted objects, to the
provided StringBuffer
.
The text substituted for the individual format elements is derived from
the current subformat of the format element and the
arguments
element at the format element's argument index
as indicated by the first matching line of the following table. An
argument is unavailable if arguments
is
null
or has fewer than argumentIndex+1 elements.
Subformat | Argument | Formatted Text |
---|---|---|
any | unavailable | "{" + argumentIndex + "}"
|
any | null
| "null"
|
instanceof ChoiceFormat
| any | subformat.format(argument).indexOf('{') >= 0 ?
|
!= null
| any | subformat.format(argument)
|
null
| instanceof Number
| NumberFormat.getInstance(getLocale()).format(argument)
|
null
| instanceof Date
| DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT, getLocale()).format(argument)
|
null
| instanceof String
| argument
|
null
| any | argument.toString()
|
If pos
is non-null, and refers to
Field.ARGUMENT
, the location of the first formatted
string will be returned.
Parameters: arguments an array of objects to be formatted and substituted. result where text is appended. pos On input: an alignment field, if desired. On output: the offsets of the alignment field.
Throws: IllegalArgumentException if an argument in the
arguments
array is not of the type
expected by the format element(s) that use it.
UNKNOWN: ICU 3.0
(new
(pattern)).MessageFormat
(java.lang.Object[], java.lang.StringBuffer, java.text.FieldPosition) format
(arguments, new StringBuffer(), null).toString()
Throws: IllegalArgumentException if the pattern is invalid,
or if an argument in the arguments
array
is not of the type expected by the format element(s)
that use it.
UNKNOWN: ICU 3.0
MessageFormat
's
pattern, with format elements replaced by the formatted objects, to the
provided StringBuffer
.
This is equivalent to
(java.lang.Object[], java.lang.StringBuffer, java.text.FieldPosition) format
((Object[]) arguments, result, pos)
Parameters: arguments an array of objects to be formatted and substituted. result where text is appended. pos On input: an alignment field, if desired. On output: the offsets of the alignment field.
Throws: IllegalArgumentException if an argument in the
arguments
array is not of the type
expected by the format element(s) that use it.
UNKNOWN: ICU 3.0
Since the order of format elements in a pattern string often
changes during localization, it's generally better to use the
getFormatsByArgumentIndex
method, which assumes an order of formats corresponding to the
order of elements in the arguments
array passed to
the format
methods or the result array returned by
the parse
methods.
Returns: the formats used for the format elements in the pattern
UNKNOWN: ICU 3.0
format
methods or returned from parse
methods. The indices of elements in the returned array
correspond to the argument indices used in the previously set
pattern string.
The order of formats in the returned array thus corresponds to
the order of elements in the arguments
array passed
to the format
methods or the result array returned
by the parse
methods.
If an argument index is used for more than one format element in the pattern string, then the format used for the last such format element is returned in the array. If an argument index is not used for any format element in the pattern string, then null is returned in the array.
Returns: the formats used for the arguments within the pattern
UNKNOWN: ICU 3.0
Returns: the locale used when creating or comparing subformats
UNKNOWN: ICU 3.0
Returns: the locale used when creating or comparing subformats
UNKNOWN: ICU 3.2
UNKNOWN: ICU 3.0
Caveats: The parse may fail in a number of circumstances. For example:
UNKNOWN: ICU 3.0
See the MessageFormat method for more information on message parsing.
Parameters: source A String
whose beginning should be parsed.
Returns: An Object
array parsed from the string.
Throws: ParseException if the beginning of the specified string cannot be parsed.
UNKNOWN: ICU 3.0
The method attempts to parse text starting at the index given by
pos
.
If parsing succeeds, then the index of pos
is updated
to the index after the last character used (parsing does not necessarily
use all characters up to the end of the string), and the parsed
object array is returned. The updated pos
can be used to
indicate the starting point for the next call to this method.
If an error occurs, then the index of pos
is not
changed, the error index of pos
is set to the index of
the character where the error occurred, and null is returned.
See the MessageFormat method for more information on message parsing.
Parameters: source A String
, part of which should be parsed. pos A ParsePosition
object with index and error
index information as described above.
Returns: An Object
array parsed from the string. In case of
error, returns null.
Throws: NullPointerException if pos
is null.
UNKNOWN: ICU 3.0
Since the order of format elements in a pattern string often
changes during localization, it is generally better to use the
setFormatByArgumentIndex
method, which accesses format elements based on the argument
index they specify.
Parameters: formatElementIndex the index of a format element within the pattern newFormat the format to use for the specified format element
Throws: ArrayIndexOutOfBoundsException if formatElementIndex is equal to or larger than the number of format elements in the pattern string
UNKNOWN: ICU 3.0
arguments
array passed
to the format
methods or the result array returned
by the parse
methods.
If the argument index is used for more than one format element in the pattern string, then the new format is used for all such format elements. If the argument index is not used for any format element in the pattern string, then the new format is ignored.
Parameters: argumentIndex the argument index for which to use the new format newFormat the new format to use
UNKNOWN: ICU 3.0
newFormats
corresponds to
the order of format elements in the pattern string.
If more formats are provided than needed by the pattern string,
the remaining ones are ignored. If fewer formats are provided
than needed, then only the first newFormats.length
formats are replaced.
Since the order of format elements in a pattern string often
changes during localization, it is generally better to use the
setFormatsByArgumentIndex
method, which assumes an order of formats corresponding to the
order of elements in the arguments
array passed to
the format
methods or the result array returned by
the parse
methods.
Parameters: newFormats the new formats to use
Throws: NullPointerException if newFormats
is null
UNKNOWN: ICU 3.0
format
methods or returned from parse
methods. The indices of elements in newFormats
correspond to the argument indices used in the previously set
pattern string.
The order of formats in newFormats
thus corresponds to
the order of elements in the arguments
array passed
to the format
methods or the result array returned
by the parse
methods.
If an argument index is used for more than one format element
in the pattern string, then the corresponding new format is used
for all such format elements. If an argument index is not used
for any format element in the pattern string, then the
corresponding new format is ignored. If fewer formats are provided
than needed, then only the formats for argument indices less
than newFormats.length
are replaced.
Parameters: newFormats the new formats to use
Throws: NullPointerException if newFormats
is null
UNKNOWN: ICU 3.0
applyPattern
and toPattern
methods as well as to the
format
and
formatToCharacterIterator
methods.
Parameters: locale the locale to be used when creating or comparing subformats
UNKNOWN: ICU 3.0
applyPattern
and toPattern
methods as well as to the
format
and
formatToCharacterIterator
methods.
Parameters: locale the locale to be used when creating or comparing subformats
UNKNOWN: ICU 3.2
Returns: a pattern representing the current state of the message format
UNKNOWN: ICU 3.0