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Chapter 16 The java.text Package |
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Chapter 16 The java.text Package |
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java.text.MessageFormat
java.text.Format
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New as of JDK 1.1
The MessageFormat class constructs textual messages using a formatting pattern string. Conceptually, the class functions much like printf() in C. Syntactically, however, it is quite different. A MessageFormat object uses a pattern string; formatted arguments are placed into the pattern string to produce a resulting string. Arguments are delimited by matching sets of curly braces and may include additional information about how that data should be formatted. For example, consider the following code:
String message =
"Boot of server {0}began at {1, time}on {1, date, full}.";
MessageFormat boot = new MessageFormat(message);
Date now = new Date();
Object[] arguments = {"luna3", now};
System.out.println(boot.format(arguments));
This code produces the following output:
Boot of server luna3 began at 11:13:22 AM on Monday, March 03, 1997.
Each of the arguments is numbered and includes an optional type and an optional style. In the example above, {1, date, full} indicates that the argument at index 1 in the argument array should be formatted using a DateFormat object with the FULL style. The allowed types and styles are:
| Type | Object | Styles |
|---|---|---|
|
choice |
ChoiceFormat |
pattern |
|
date |
DateFormat |
short, medium, long, full, pattern |
|
number |
NumberFormat |
integer, percent, currency, pattern |
|
time |
DateFormat |
short, medium, long, full, pattern |
For the date and time types, the styles correspond to the styles, or lengths, of the resulting date and time strings. You can also specify a date or time pattern string as you would for creating a SimpleDateFormat object. For the number type, the styles correspond to formatting normal numbers, percentage values, and currency values. You can also specify a number pattern string as you would for creating a DecimalFormat object. For the choice type, you can specify a choice pattern as you would for creating a ChoiceFormat object. If no type is specified, the argument should be a string.
The following example shows how to use a choice format pattern with a MessageFormat:
Object[] arguments = {new Integer(1)};
String grammar = "At last count, {0}server{0, choice, 0#s|1#|1<s}
{0, choice, 0#were|1#was|1<were}booted.";
MessageFormat booted = new MessageFormat(grammar);
System.out.println(booted.format(arguments));
arguments[0] = new Integer(2);
System.out.println(booted.format(arguments));
This example produces the following output:
At last count, 1 server was booted. At last count, 2 servers were booted.
As an alternative to specifying all of the formatting in the pattern string, you can use an array of Format objects to format the arguments. You can specify this array using setFormats().
Note that you create MessageFormat objects directly, rather than through factory methods. This is because MessageFormat does not implement any locale-specific behavior. To produce properly internationalized output, the pattern string that is used to construct a MessageFormat should come from a ResourceBundle instead of being embedded in the code.
public class java.text.MessageFormat extends java.text.Format {
// Constructors
public MessageFormat(String pattern);
// Class Methods
public static String format(String pattern, Object[] arguments);
// Instance Methods
public void applyPattern(String newPattern);
public Object clone();
public boolean equals(Object obj);
public final StringBuffer format(Object source, StringBuffer result,
FieldPosition ignore);
public final StringBuffer format(Object[] source, StringBuffer result,
FieldPosition ignore);
public Format[] getFormats();
public Locale getLocale();
public int hashCode();
public Object[] parse(String source);
public Object[] parse(String source, ParsePosition status);
public Object parseObject(String text, ParsePosition status);
public void setFormat(int variable, Format newFormat);
public void setFormats(Format[] newFormats);
public void setLocale(Locale theLocale);
public String toPattern();
}
The pattern string.
This constructor creates a MessageFormat with the given formatting pattern string.
The pattern string.
An array of arguments.
Calling this static method is equivalent to constructing a MessageFormat using the given formatting pattern string and asking it to format the given arguments with the format() method.
The pattern string.
This method tells this MessageFormat to use the given formatting pattern to format and parse arguments.
A copy of this MessageFormat.
Format.clone()
This method creates a copy of this MessageFormat and then returns it.
The object to be compared with this object.
true if the objects are equal; false if they are not.
Format.equals()
This method returns true if obj is an instance of MessageFormat and is equivalent to this MessageFormat.
public StringBuffer format(Object source, StringBuffer result, FieldPosition ignore)
The object to be formatted.
A StringBuffer on which to append the formatted information.
Ignored.
The given buffer result with the formatted representation of the object appended to it.
Format.format(Object, StringBuffer, FieldPosition)
This method formats the given object and appends the result to the given StringBuffer. The method assumes that the given object is an array of arguments.
public StringBuffer format(Object[] source, StringBuffer result, FieldPosition ignore)
The object array to be formatted.
A StringBuffer on which to append the formatted information.
Ignored.
The given buffer result with the formatted representation of the object array appended to it.
This method formats the given arguments in the object array and appends the result to the given StringBuffer.
An array of the formats used by this MessageFormat.
This method returns the format objects that this MessageFormat uses. Note that formats are numbered according to the order in which they appear in the formatting pattern string, not according to their specified argument numbers.
The Locale of this MessageFormat.
This method returns the locate for this MessageFormat. This locale is used to get default date, time, and number formatters.
A hashcode for this object.
Object.hashCode()
This method returns a hashcode for this MessageFormat.
The string to be parsed.
An array of objects represented by the given string.
If the text cannot be parsed.
This method parses arguments from the given string, which should be in the format given by the formatting pattern string of this MessageFormat. If the string is not correctly formatted, an exception is thrown.
The string to be parsed.
A ParsePosition object that specifies a position in the string.
An array of objects represented by the test starting at the given position.
This method parses arguments from the given string, starting at the specified position. The string should be in the format given by the formatting pattern string of this MessageFormat.
The string to be parsed.
A ParsePosition object that specifies a position in the string.
The object represented by the test starting at the given position.
Format.parseObject(String, ParsePosition)
This method parses arguments from the given string, starting at the specified position. The string should be in the format given by the formatting pattern string of this MessageFormat.
The index of an argument in the pattern string.
The format object to use.
This method sets the Format object that is used for the given argument in the formatting pattern string.
The format objects to use.
This method sets the Format objects that format the arguments of this MessageFormat. Note that formats are numbered according to the order in which they appear in the formatting pattern string, not according to their specified argument numbers.
The new locale.
This method sets the Locale object that generates the default date, time, and number format objects.
The pattern string of this MessageFormat.
This method returns the pattern string of this MessageFormat.
| Method | Inherited From | Method | Inherited From |
|---|---|---|---|
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finalize() |
Object |
format(Object) |
Format |
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getClass() |
Object |
notify() |
Object |
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notifyAll() |
Object |
parseObject(String) |
Format |
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toString() |
Object |
wait() |
Object |
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wait(long) |
Object |
wait(long, int) |
Object |
ChoiceFormat, DateFormat, FieldPosition, Format, Locale, NumberFormat, ParseException, ParsePosition, ResourceBundle, String, StringBuffer
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| Format |  |
NumberFormat |
