@NotThreadSafe public final class MessageFormat extends Format
MessageFormat provides a means to produce concatenated messages in a language-neutral way. Use this to
construct messages displayed for end users.
this implementation is based on java.text.MessageFormat with the goal to be a faster and more flexible implementation
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 sub-formats
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
Within a String, a pair of single quotes can be used to quote any arbitrary characters except single quotes.
For example, pattern string "'{0}'" represents string "{0}", not a FormatElement. A
single quote itself must be represented by doubled single quotes '' throughout a
String. For example, pattern string "'{''}'" is interpreted as a sequence of '{
(start of quoting and a left curly brace), '' (a single quote), and }' (a right curly brace
and end of quoting),
not '{' and '}' (quoted left and right curly braces): representing string
"{'}",
not "{}".
A SubformatPattern is interpreted by its corresponding sub-format, and sub-format-dependent pattern rules
apply. For example, pattern string "{1,number,$'#',##}" (SubformatPattern with underline)
will produce a number format with the pound-sign quoted, with a result such as: "$#31,45". Refer to each Format subclass documentation for details.
Any unmatched quote is treated as closed at the end of the given pattern. For example, pattern string "'{0}"
is treated as pattern "'{0}'".
Any curly braces within an unquoted pattern must be balanced. For example, "ab {0} de" and
"ab '}' de" are valid patterns, but "ab {0'}' de", "ab } de" and
"''{''" are not.
MessageFormat. Note that localizers may need to use single
quotes in translated strings where the original version doesn't have them.
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.
Here are some examples of usage. In real internationalized programs, the message format pattern and other static strings will, of course, be obtained from resource bundles. Other parameters will be dynamically determined at runtime.
The first example uses the static method MessageFormat.format, which internally creates a
MessageFormat for one-time use:
int planet = 7;
String event = "a disturbance in the Force";
String result = MessageFormat.format(
"At {1,time} on {1,date}, there was {2} on planet {0,number,integer}.",
planet, new Date(), event);
At 12:30 PM on Jul 3, 2053, there was a disturbance in the Force on planet 7.
The following example creates a MessageFormat instance that can be used repeatedly:
int fileCount = 1273;
String diskName = "MyDisk";
Object[] testArgs = {new Long(fileCount), diskName};
MessageFormat form = new MessageFormat(
"The disk \"{1}\" contains {0} file(s).");
System.out.println(form.format(testArgs));
fileCount:
The disk "MyDisk" contains 0 file(s). The disk "MyDisk" contains 1 file(s). The disk "MyDisk" contains 1,273 file(s).
For more sophisticated patterns, you can use a ChoiceFormat to produce correct forms for singular and
plural:
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);
int fileCount = 1273;
String diskName = "MyDisk";
Object[] testArgs = {new Long(fileCount), diskName};
System.out.println(form.format(testArgs));
fileCount:
The disk "MyDisk" contains no files. The disk "MyDisk" contains one file. The disk "MyDisk" contains 1,273 files.
You can create the ChoiceFormat programmatically, as in the above example, or by using a pattern. See
ChoiceFormat for more information.
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 as special; occurrences of '{' are used to indicate 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 occurrences 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.
Locale,
Format,
NumberFormat,
DecimalFormat,
DecimalFormatSymbols,
ChoiceFormat,
DateFormat,
SimpleDateFormat,
Serialized FormFormat.Field| Constructor and Description |
|---|
MessageFormat(String pattern)
Constructs a FastMessageFormat for the default
FORMAT locale and the
specified pattern. |
MessageFormat(String pattern,
Locale locale)
Constructs a FastMessageFormat for the specified locale and pattern.
|
| Modifier and Type | Method and Description |
|---|---|
void |
applyPattern(String pattern)
Sets the pattern used by this message format.
|
MessageFormat |
clone()
Creates and returns a copy of this object.
|
boolean |
equals(Object obj)
Equality comparison between two message format objects
|
<T extends CharSequence & Appendable> |
format(Object[] arguments,
T result) |
<T extends CharSequence & Appendable> |
format(Object[] arguments,
T 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. |
StringBuffer |
format(Object obj,
StringBuffer toAppendTo,
FieldPosition pos) |
<T extends CharSequence & Appendable> |
format(Object arguments,
T 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.
|
AttributedCharacterIterator |
formatToCharacterIterator(Object arguments)
Formats an array of objects and inserts them into the
MessageFormat's pattern, producing an
AttributedCharacterIterator. |
Format[] |
getFormats()
Gets the formats used for the format elements in the previously set pattern string.
|
Locale |
getLocale()
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)
Parses text from the beginning of the given string to produce an object array.
|
Object[] |
parse(String source,
ParsePosition pos)
Parses the string.
|
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.
|
String |
toPattern()
Returns a pattern representing the current state of the message format.
|
String |
toString() |
format, parseObjectpublic MessageFormat(String pattern)
FORMAT locale and the
specified pattern. The constructor first sets the locale, then parses the pattern and creates a list of subformats
for the format elements contained in it. Patterns and their interpretation are specified in the
class description.pattern - the pattern for this message formatIllegalArgumentException - if the pattern is invalidpublic MessageFormat(String pattern, Locale locale)
pattern - the pattern for this message formatlocale - the locale for this message formatIllegalArgumentException - if the pattern is invalidpublic void setLocale(Locale locale)
applyPattern and toPattern methods if format elements specify a
format type and therefore have the subformats created in the applyPattern method, as well as
format and formatToCharacterIterator methods if format
elements do not specify a format type and therefore have the subformats created in the formatting methods.
locale - the locale to be used when creating or comparing subformatspublic Locale getLocale()
public void applyPattern(String pattern)
pattern - the pattern for this message formatIllegalArgumentException - if the pattern is invalidpublic String toPattern()
public void setFormatsByArgumentIndex(Format[] newFormats)
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.
newFormats - the new formats to useNullPointerException - if newFormats is nullpublic void setFormats(Format[] newFormats)
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.
newFormats - the new formats to useNullPointerException - if newFormats is nullpublic void setFormatByArgumentIndex(int argumentIndex,
Format newFormat)
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.
argumentIndex - the argument index for which to use the new formatnewFormat - the new format to usepublic void setFormat(int formatElementIndex,
Format newFormat)
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.
formatElementIndex - the index of a format element within the patternnewFormat - the format to use for the specified format elementArrayIndexOutOfBoundsException - if formatElementIndex is equal to or larger than the number of
format elements in the pattern stringpublic Format[] getFormats()
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.
public final <T extends CharSequence & Appendable> T format(Object[] arguments, T result, @Nullable FieldPosition pos) throws IOException
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.
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.result, with formatted text appendedIllegalArgumentException - if an argument in the arguments array is not of the type expected
by the format element(s) that use it.IOExceptionpublic final <T extends CharSequence & Appendable> T format(Object[] arguments, T result) throws IOException
IOExceptionpublic static String format(String pattern, Object... arguments)
(new MessageFormat(pattern)).format(arguments,
new StringBuffer(), null).toString()
pattern - the pattern stringarguments - object(s) to formatIllegalArgumentException - 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.public final <T extends CharSequence & Appendable> T format(Object arguments, T result, FieldPosition pos) throws IOException
MessageFormat's pattern, with format elements replaced by
the formatted objects, to the provided StringBuffer. This is equivalent to
format((Object[])
arguments, result, pos)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.IllegalArgumentException - if an argument in the arguments array is not of the type expected
by the format element(s) that use it.IOExceptionpublic AttributedCharacterIterator formatToCharacterIterator(@Nonnull Object arguments)
MessageFormat's pattern, producing an
AttributedCharacterIterator. You can use the returned AttributedCharacterIterator to
build the resulting String, as well as to determine information about the resulting String.
The text of the returned AttributedCharacterIterator is the same that would be returned by
format(arguments, new
StringBuffer(), null).toString()
In addition, the AttributedCharacterIterator contains at least attributes indicating where text was
generated from an argument in the arguments array. The keys of these attributes are of type
MessageFormat.Field, their values are Integer objects indicating the index in the
arguments array of the argument from which the text was generated.
The attributes/value from the underlying Format instances that MessageFormat uses will
also be placed in the resulting AttributedCharacterIterator. This allows you to not only find where an
argument is placed in the resulting String, but also which fields it contains in turn.
formatToCharacterIterator in class Formatarguments - an array of objects to be formatted and substituted.NullPointerException - if arguments is null.IllegalArgumentException - if an argument in the arguments array is not of the type expected
by the format element(s) that use it.@Nullable public Object[] parse(@Nullable String source, @Nonnull ParsePosition pos)
Caveats: The parse may fail in a number of circumstances. For example:
source - the string to parsepos - the parse position@Nullable public Object[] parse(String source) throws ParseException
See the parse(String, ParsePosition) method for more information on message parsing.
source - A String whose beginning should be parsed.Object array parsed from the string.ParseException - if the beginning of the specified string cannot be parsed.@Nullable public Object parseObject(String source, ParsePosition pos)
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 parse(String, ParsePosition) method for more information on message parsing.
parseObject in class Formatsource - A String, part of which should be parsed.pos - A ParsePosition object with index and error index information as described above.Object array parsed from the string. In case of error, returns null.NullPointerException - if pos is null.public MessageFormat clone()
public boolean equals(Object obj)
public int hashCode()
public StringBuffer format(Object obj, StringBuffer toAppendTo, FieldPosition pos)
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