java.text: abstract public class: Format

java.text
abstract public class: Format [javadoc | source]

java.lang.Object
   java.text.Format

All Implemented Interfaces:
Cloneable, Serializable

Direct Known Subclasses:
DateFormat, NumberFormat, ChoiceFormat, DecimalFormat, MessageFormat, SimpleDateFormat

Format is an abstract base class for formatting locale-sensitive information such as dates, messages, and numbers.

Format defines the programming interface for formatting locale-sensitive objects into Strings (the format method) and for parsing Strings back into objects (the parseObject method).

Generally, a format's parseObject method must be able to parse any string formatted by its format method. However, there may be exceptional cases where this is not possible. For example, a format method might create two adjacent integer numbers with no separator in between, and in this case the parseObject could not tell which digits belong to which number.

Subclassing

The Java Platform provides three specialized subclasses of Format-- DateFormat, MessageFormat, and NumberFormat--for formatting dates, messages, and numbers, respectively.

Concrete subclasses must implement three methods:

format(Object obj, StringBuffer toAppendTo, FieldPosition pos)
formatToCharacterIterator(Object obj)
parseObject(String source, ParsePosition pos)

These general methods allow polymorphic parsing and formatting of objects and are used, for example, by MessageFormat. Subclasses often also provide additional format methods for specific input types as well as parse methods for specific result types. Any parse method that does not take a ParsePosition argument should throw ParseException when no text in the required format is at the beginning of the input text.

Most subclasses will also implement the following factory methods:

getInstance for getting a useful format object appropriate for the current locale
getInstance(Locale) for getting a useful format object appropriate for the specified locale

In addition, some subclasses may also implement other getXxxxInstance methods for more specialized control. For example, the NumberFormat class provides getPercentInstance and getCurrencyInstance methods for getting specialized number formatters.

Subclasses of Format that allow programmers to create objects for locales (with getInstance(Locale) for example) must also implement the following class method:

public static Locale[] getAvailableLocales()

And finally subclasses may define a set of constants to identify the various fields in the formatted output. These constants are used to create a FieldPosition object which identifies what information is contained in the field and its position in the formatted result. These constants should be named item_FIELD where item identifies the field. For examples of these constants, see ERA_FIELD and its friends in DateFormat .

Synchronization

Formats are generally 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.

Also see:

java.text.ParsePosition

java.text.FieldPosition

java.text.NumberFormat

java.text.DateFormat

java.text.MessageFormat

author: Mark - Davis

Nested Class Summary:
public static class	Format.Field	Defines constants that are used as attribute keys in the `AttributedCharacterIterator` returned from `Format.formatToCharacterIterator` and as field identifiers in `FieldPosition`.
interface	Format.FieldDelegate	FieldDelegate is notified by the various `Format` implementations as they are formatting the Objects. This allows for storage of the individual sections of the formatted String for later use, such as in a `FieldPosition` or for an `AttributedCharacterIterator`. Delegates should NOT assume that the `Format` will notify the delegate of fields in any particular order.

Constructor:
protected Format() { } Sole constructor. (For invocation by subclass constructors, typically implicit.)

Constructor:

 protected Format() {

}

Sole constructor. (For invocation by subclass constructors, typically implicit.)

Method from java.text.Format Summary:
clone, createAttributedCharacterIterator, createAttributedCharacterIterator, createAttributedCharacterIterator, createAttributedCharacterIterator, format, format, formatToCharacterIterator, parseObject, parseObject

Methods from java.lang.Object:
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from java.text.Format Detail:
public Object clone() { try { return super.clone(); } catch (CloneNotSupportedException e) { // will never happen return null; } } Creates and returns a copy of this object.
AttributedCharacterIterator createAttributedCharacterIterator(String s) { AttributedString as = new AttributedString(s); return as.getIterator(); } Creates an `AttributedCharacterIterator` for the String `s`.
AttributedCharacterIterator createAttributedCharacterIterator(AttributedCharacterIterator[] iterators) { AttributedString as = new AttributedString(iterators); return as.getIterator(); } Creates an `AttributedCharacterIterator` containg the concatenated contents of the passed in `AttributedCharacterIterator`s.
AttributedCharacterIterator createAttributedCharacterIterator(String string, Attribute key, Object value) { AttributedString as = new AttributedString(string); as.addAttribute(key, value); return as.getIterator(); } Returns an AttributedCharacterIterator with the String `string` and additional key/value pair `key`, `value`.
AttributedCharacterIterator createAttributedCharacterIterator(AttributedCharacterIterator iterator, Attribute key, Object value) { AttributedString as = new AttributedString(iterator); as.addAttribute(key, value); return as.getIterator(); } Creates an AttributedCharacterIterator with the contents of `iterator` and the additional attribute `key` `value`.
public final String format(Object obj) { return format(obj, new StringBuffer(), new FieldPosition(0)).toString(); } Formats an object to produce a string. This is equivalent to format `(obj, new StringBuffer(), new FieldPosition(0)).toString();`
abstract public StringBuffer format(Object obj, StringBuffer toAppendTo, FieldPosition pos) Formats an object and appends the resulting text to a given string buffer. If the `pos` argument identifies a field used by the format, then its indices are set to the beginning and end of the first such field encountered.
public AttributedCharacterIterator formatToCharacterIterator(Object obj) { return createAttributedCharacterIterator(format(obj)); } Formats an Object producing an `AttributedCharacterIterator`. You can use the returned `AttributedCharacterIterator` to build the resulting String, as well as to determine information about the resulting String. Each attribute key of the AttributedCharacterIterator will be of type `Field`. It is up to each `Format` implementation to define what the legal values are for each attribute in the `AttributedCharacterIterator`, but typically the attribute key is also used as the attribute value. The default implementation creates an `AttributedCharacterIterator` with no attributes. Subclasses that support fields should override this and create an `AttributedCharacterIterator` with meaningful attributes.
public Object parseObject(String source) throws ParseException { ParsePosition pos = new ParsePosition(0); Object result = parseObject(source, pos); if (pos.index == 0) { throw new ParseException("Format.parseObject(String) failed", pos.errorIndex); } return result; } Parses text from the beginning of the given string to produce an object. The method may not use the entire text of the given string.
abstract public Object parseObject(String source, ParsePosition pos) Parses text from a string to produce an object. 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 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.

Method from java.text.Format Detail:

 public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            // will never happen
            return null;
        }
}

Creates and returns a copy of this object.

 AttributedCharacterIterator createAttributedCharacterIterator(String s) {
        AttributedString as = new AttributedString(s);
        return as.getIterator();
}

AttributedCharacterIterator

s

 AttributedCharacterIterator createAttributedCharacterIterator(AttributedCharacterIterator[] iterators) {
        AttributedString as = new AttributedString(iterators);
        return as.getIterator();
}

AttributedCharacterIterator

 AttributedCharacterIterator createAttributedCharacterIterator(String string,
    Attribute key,
    Object value) {
        AttributedString as = new AttributedString(string);
        as.addAttribute(key, value);
        return as.getIterator();
}

string

key

value

 AttributedCharacterIterator createAttributedCharacterIterator(AttributedCharacterIterator iterator,
    Attribute key,
    Object value) {
        AttributedString as = new AttributedString(iterator);
        as.addAttribute(key, value);
        return as.getIterator();
}

iterator

key

value

 public final String format(Object obj) {
        return format(obj, new StringBuffer(), new FieldPosition(0)).toString();
}

format (obj, new StringBuffer(), new FieldPosition(0)).toString();

 abstract public StringBuffer format(Object obj,
    StringBuffer toAppendTo,
    FieldPosition pos)Formats an object and appends the resulting text to a given string
buffer.
If the pos argument identifies a field used by the format,
then its indices are set to the beginning and end of the first such
field encountered.

 public AttributedCharacterIterator formatToCharacterIterator(Object obj) {
        return createAttributedCharacterIterator(format(obj));
}

AttributedCharacterIterator

Each attribute key of the AttributedCharacterIterator will be of type Field. It is up to each Format implementation to define what the legal values are for each attribute in the AttributedCharacterIterator, but typically the attribute key is also used as the attribute value.

The default implementation creates an AttributedCharacterIterator with no attributes. Subclasses that support fields should override this and create an AttributedCharacterIterator with meaningful attributes.

 public Object parseObject(String source) throws ParseException {
        ParsePosition pos = new ParsePosition(0);
        Object result = parseObject(source, pos);
        if (pos.index == 0) {
            throw new ParseException("Format.parseObject(String) failed",
                pos.errorIndex);
        }
        return result;
}

Parses text from the beginning of the given string to produce an object. The method may not use the entire text of the given string.

 abstract public Object parseObject(String source,
    ParsePosition pos)Parses text from a string to produce an object.

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 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.