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/*
* (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
* (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved
*
* The original version of this source code and documentation is copyrighted
* and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
* materials are provided under terms of a License Agreement between Taligent
* and Sun. This technology is protected by multiple US and International
* patents. This notice and attribution to Taligent may not be removed.
* Taligent is a registered trademark of Taligent, Inc.
*
*/
package java.text;
import java.io.Serializable;
/**
* <code>Format</code> is an abstract base class for formatting locale-sensitive
* information such as dates, messages, and numbers.
*
* <p>
* <code>Format</code> defines the programming interface for formatting
* locale-sensitive objects into <code>String</code>s (the
* <code>format</code> method) and for parsing <code>String</code>s back
* into objects (the <code>parseObject</code> method).
*
* <p>
* Generally, a format's <code>parseObject</code> method must be able to parse
* any string formatted by its <code>format</code> method. However, there may
* be exceptional cases where this is not possible. For example, a
* <code>format</code> method might create two adjacent integer numbers with
* no separator in between, and in this case the <code>parseObject</code> could
* not tell which digits belong to which number.
*
* <h3>Subclassing</h3>
*
* <p>
* The Java Platform provides three specialized subclasses of <code>Format</code>--
* <code>DateFormat</code>, <code>MessageFormat</code>, and
* <code>NumberFormat</code>--for formatting dates, messages, and numbers,
* respectively.
* <p>
* Concrete subclasses must implement three methods:
* <ol>
* <li> <code>format(Object obj, StringBuffer toAppendTo, FieldPosition pos)</code>
* <li> <code>formatToCharacterIterator(Object obj)</code>
* <li> <code>parseObject(String source, ParsePosition pos)</code>
* </ol>
* These general methods allow polymorphic parsing and formatting of objects
* and are used, for example, by <code>MessageFormat</code>.
* Subclasses often also provide additional <code>format</code> methods for
* specific input types as well as <code>parse</code> methods for specific
* result types. Any <code>parse</code> method that does not take a
* <code>ParsePosition</code> argument should throw <code>ParseException</code>
* when no text in the required format is at the beginning of the input text.
*
* <p>
* Most subclasses will also implement the following factory methods:
* <ol>
* <li>
* <code>getInstance</code> for getting a useful format object appropriate
* for the current locale
* <li>
* <code>getInstance(Locale)</code> for getting a useful format
* object appropriate for the specified locale
* </ol>
* In addition, some subclasses may also implement other
* <code>getXxxxInstance</code> methods for more specialized control. For
* example, the <code>NumberFormat</code> class provides
* <code>getPercentInstance</code> and <code>getCurrencyInstance</code>
* methods for getting specialized number formatters.
*
* <p>
* Subclasses of <code>Format</code> that allow programmers to create objects
* for locales (with <code>getInstance(Locale)</code> for example)
* must also implement the following class method:
* <blockquote>
* <pre>
* public static Locale[] getAvailableLocales()
* </pre>
* </blockquote>
*
* <p>
* 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
* <code><em>item</em>_FIELD</code> where <code><em>item</em></code> identifies
* the field. For examples of these constants, see <code>ERA_FIELD</code> and its
* friends in {@link DateFormat}.
*
* <h4><a name="synchronization">Synchronization</a></h4>
*
* <p>
* 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.
*
* @see java.text.ParsePosition
* @see java.text.FieldPosition
* @see java.text.NumberFormat
* @see java.text.DateFormat
* @see java.text.MessageFormat
* @author Mark Davis
*/
public abstract class Format implements Serializable, Cloneable {
private static final long serialVersionUID = -299282585814624189L;
/**
* Sole constructor. (For invocation by subclass constructors, typically
* implicit.)
*/
protected Format() {
}
/**
* Formats an object to produce a string. This is equivalent to
* <blockquote>
* {@link #format(Object, StringBuffer, FieldPosition) format}<code>(obj,
* new StringBuffer(), new FieldPosition(0)).toString();</code>
* </blockquote>
*
* @param obj The object to format
* @return Formatted string.
* @exception IllegalArgumentException if the Format cannot format the given
* object
*/
public final String format (Object obj) {
return format(obj, new StringBuffer(), new FieldPosition(0)).toString();
}
/**
* Formats an object and appends the resulting text to a given string
* buffer.
* If the <code>pos</code> argument identifies a field used by the format,
* then its indices are set to the beginning and end of the first such
* field encountered.
*
* @param obj The object to format
* @param toAppendTo where the text is to be appended
* @param pos A <code>FieldPosition</code> identifying a field
* in the formatted text
* @return the string buffer passed in as <code>toAppendTo</code>,
* with formatted text appended
* @exception NullPointerException if <code>toAppendTo</code> or
* <code>pos</code> is null
* @exception IllegalArgumentException if the Format cannot format the given
* object
*/
public abstract StringBuffer format(Object obj,
StringBuffer toAppendTo,
FieldPosition pos);
/**
* Formats an Object producing an <code>AttributedCharacterIterator</code>.
* You can use the returned <code>AttributedCharacterIterator</code>
* to build the resulting String, as well as to determine information
* about the resulting String.
* <p>
* Each attribute key of the AttributedCharacterIterator will be of type
* <code>Field</code>. It is up to each <code>Format</code> implementation
* to define what the legal values are for each attribute in the
* <code>AttributedCharacterIterator</code>, but typically the attribute
* key is also used as the attribute value.
* <p>The default implementation creates an
* <code>AttributedCharacterIterator</code> with no attributes. Subclasses
* that support fields should override this and create an
* <code>AttributedCharacterIterator</code> with meaningful attributes.
*
* @exception NullPointerException if obj is null.
* @exception IllegalArgumentException when the Format cannot format the
* given object.
* @param obj The object to format
* @return AttributedCharacterIterator describing the formatted value.
* @since 1.4
*/
public AttributedCharacterIterator formatToCharacterIterator(Object obj) {
return createAttributedCharacterIterator(format(obj));
}
/**
* Parses text from a string to produce an object.
* <p>
* The method attempts to parse text starting at the index given by
* <code>pos</code>.
* If parsing succeeds, then the index of <code>pos</code> 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 <code>pos</code> can be used to
* indicate the starting point for the next call to this method.
* If an error occurs, then the index of <code>pos</code> is not
* changed, the error index of <code>pos</code> is set to the index of
* the character where the error occurred, and null is returned.
*
* @param source A <code>String</code>, part of which should be parsed.
* @param pos A <code>ParsePosition</code> object with index and error
* index information as described above.
* @return An <code>Object</code> parsed from the string. In case of
* error, returns null.
* @throws NullPointerException if {@code source} or {@code pos} is null.
*/
public abstract Object parseObject (String source, ParsePosition pos);
/**
* 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.
*
* @param source A <code>String</code> whose beginning should be parsed.
* @return An <code>Object</code> parsed from the string.
* @exception ParseException if the beginning of the specified string
* cannot be parsed.
* @throws NullPointerException if {@code source} is null.
*/
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;
}
/**
* Creates and returns a copy of this object.
*
* @return a clone of this instance.
*/
public Object clone() {
try {
return super.clone();
} catch (CloneNotSupportedException e) {
// will never happen
throw new InternalError(e);
}
}
//
// Convenience methods for creating AttributedCharacterIterators from
// different parameters.
//
/**
* Creates an <code>AttributedCharacterIterator</code> for the String
* <code>s</code>.
*
* @param s String to create AttributedCharacterIterator from
* @return AttributedCharacterIterator wrapping s
*/
AttributedCharacterIterator createAttributedCharacterIterator(String s) {
AttributedString as = new AttributedString(s);
return as.getIterator();
}
/**
* Creates an <code>AttributedCharacterIterator</code> containing the
* concatenated contents of the passed in
* <code>AttributedCharacterIterator</code>s.
*
* @param iterators AttributedCharacterIterators used to create resulting
* AttributedCharacterIterators
* @return AttributedCharacterIterator wrapping passed in
* AttributedCharacterIterators
*/
AttributedCharacterIterator createAttributedCharacterIterator(
AttributedCharacterIterator[] iterators) {
AttributedString as = new AttributedString(iterators);
return as.getIterator();
}
/**
* Returns an AttributedCharacterIterator with the String
* <code>string</code> and additional key/value pair <code>key</code>,
* <code>value</code>.
*
* @param string String to create AttributedCharacterIterator from
* @param key Key for AttributedCharacterIterator
* @param value Value associated with key in AttributedCharacterIterator
* @return AttributedCharacterIterator wrapping args
*/
AttributedCharacterIterator createAttributedCharacterIterator(
String string, AttributedCharacterIterator.Attribute key,
Object value) {
AttributedString as = new AttributedString(string);
as.addAttribute(key, value);
return as.getIterator();
}
/**
* Creates an AttributedCharacterIterator with the contents of
* <code>iterator</code> and the additional attribute <code>key</code>
* <code>value</code>.
*
* @param iterator Initial AttributedCharacterIterator to add arg to
* @param key Key for AttributedCharacterIterator
* @param value Value associated with key in AttributedCharacterIterator
* @return AttributedCharacterIterator wrapping args
*/
AttributedCharacterIterator createAttributedCharacterIterator(
AttributedCharacterIterator iterator,
AttributedCharacterIterator.Attribute key, Object value) {
AttributedString as = new AttributedString(iterator);
as.addAttribute(key, value);
return as.getIterator();
}
/**
* Defines constants that are used as attribute keys in the
* <code>AttributedCharacterIterator</code> returned
* from <code>Format.formatToCharacterIterator</code> and as
* field identifiers in <code>FieldPosition</code>.
*
* @since 1.4
*/
public static class Field extends AttributedCharacterIterator.Attribute {
// Proclaim serial compatibility with 1.4 FCS
private static final long serialVersionUID = 276966692217360283L;
/**
* Creates a Field with the specified name.
*
* @param name Name of the attribute
*/
protected Field(String name) {
super(name);
}
}
/**
* FieldDelegate is notified by the various <code>Format</code>
* 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 <code>FieldPosition</code> or for an
* <code>AttributedCharacterIterator</code>.
* <p>
* Delegates should NOT assume that the <code>Format</code> will notify
* the delegate of fields in any particular order.
*
* @see FieldPosition#getFieldDelegate
* @see CharacterIteratorFieldDelegate
*/
interface FieldDelegate {
/**
* Notified when a particular region of the String is formatted. This
* method will be invoked if there is no corresponding integer field id
* matching <code>attr</code>.
*
* @param attr Identifies the field matched
* @param value Value associated with the field
* @param start Beginning location of the field, will be >= 0
* @param end End of the field, will be >= start and <= buffer.length()
* @param buffer Contains current formatted value, receiver should
* NOT modify it.
*/
public void formatted(Format.Field attr, Object value, int start,
int end, StringBuffer buffer);
/**
* Notified when a particular region of the String is formatted.
*
* @param fieldID Identifies the field by integer
* @param attr Identifies the field matched
* @param value Value associated with the field
* @param start Beginning location of the field, will be >= 0
* @param end End of the field, will be >= start and <= buffer.length()
* @param buffer Contains current formatted value, receiver should
* NOT modify it.
*/
public void formatted(int fieldID, Format.Field attr, Object value,
int start, int end, StringBuffer buffer);
}
}