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package java.text;

import java.io.Serializable;


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:

    

  1.  format(Object obj, StringBuffer toAppendTo, FieldPosition pos) 
  2.  formatToCharacterIterator(Object obj) 
  3.  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:

    

  1.  getInstance for getting a useful format object appropriate for the current locale 
  2.  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.

Author:      Mark Davis
See Also:
Since:1.1
/**
 * {@code Format} is an abstract base class for formatting locale-sensitive
 * information such as dates, messages, and numbers.
 *
 * <p>
 * {@code Format} defines the programming interface for formatting
 * locale-sensitive objects into {@code String}s (the
 * {@code format} method) and for parsing {@code String}s back
 * into objects (the {@code parseObject} method).
 *
 * <p>
 * Generally, a format's {@code parseObject} method must be able to parse
 * any string formatted by its {@code format} method. However, there may
 * be exceptional cases where this is not possible. For example, a
 * {@code format} method might create two adjacent integer numbers with
 * no separator in between, and in this case the {@code parseObject} could
 * not tell which digits belong to which number.
 *
 * <h2>Subclassing</h2>
 *
 * <p>
 * The Java Platform provides three specialized subclasses of {@code Format}--
 * {@code DateFormat}, {@code MessageFormat}, and
 * {@code NumberFormat}--for formatting dates, messages, and numbers,
 * respectively.
 * <p>
 * Concrete subclasses must implement three methods:
 * <ol>
 * <li> {@code format(Object obj, StringBuffer toAppendTo, FieldPosition pos)}
 * <li> {@code formatToCharacterIterator(Object obj)}
 * <li> {@code parseObject(String source, ParsePosition pos)}
 * </ol>
 * These general methods allow polymorphic parsing and formatting of objects
 * and are used, for example, by {@code MessageFormat}.
 * Subclasses often also provide additional {@code format} methods for
 * specific input types as well as {@code parse} methods for specific
 * result types. Any {@code parse} method that does not take a
 * {@code ParsePosition} argument should throw {@code ParseException}
 * 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} for getting a useful format object appropriate
 * for the current locale
 * <li>
 * {@code getInstance(Locale)} for getting a useful format
 * object appropriate for the specified locale
 * </ol>
 * In addition, some subclasses may also implement other
 * {@code getXxxxInstance} methods for more specialized control. For
 * example, the {@code NumberFormat} class provides
 * {@code getPercentInstance} and {@code getCurrencyInstance}
 * methods for getting specialized number formatters.
 *
 * <p>
 * Subclasses of {@code Format} that allow programmers to create objects
 * for locales (with {@code getInstance(Locale)} 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} and its
 * friends in {@link DateFormat}.
 *
 * <h3><a id="synchronization">Synchronization</a></h3>
 *
 * <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
 * @since 1.1
 */
public abstract class Format implements Serializable, Cloneable {

    @java.io.Serial
    private static final long serialVersionUID = -299282585814624189L;

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

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

    
Formats an object to produce a string. This is equivalent to

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



Params:
  • obj –    The object to format
Throws:
Returns:      Formatted string.
/**
     * 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.
     * @throws    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 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. 
Params:
  • obj –    The object to format
  • toAppendTo –    where the text is to be appended
  • pos –  A FieldPosition identifying a field in the formatted text
Throws:
Returns: the string buffer passed in as toAppendTo, with formatted text appended
/**
     * Formats an object and appends the resulting text to a given string
     * buffer.
     * If the {@code 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.
     *
     * @param obj    The object to format
     * @param toAppendTo    where the text is to be appended
     * @param pos    A {@code FieldPosition} identifying a field
     *               in the formatted text
     * @return       the string buffer passed in as {@code toAppendTo},
     *               with formatted text appended
     * @throws    NullPointerException if {@code toAppendTo} or
     *            {@code pos} is null
     * @throws    IllegalArgumentException if the Format cannot format the given
     *            object
     */
    public abstract StringBuffer format(Object obj,
                    StringBuffer toAppendTo,
                    FieldPosition pos);

    
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. 
Params:
  • obj – The object to format
Throws:
Returns:AttributedCharacterIterator describing the formatted value.
Since:1.4
/**
     * Formats an Object producing an {@code AttributedCharacterIterator}.
     * You can use the returned {@code AttributedCharacterIterator}
     * 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}. It is up to each {@code Format} implementation
     * to define what the legal values are for each attribute in the
     * {@code AttributedCharacterIterator}, but typically the attribute
     * key is also used as the attribute value.
     * <p>The default implementation creates an
     * {@code AttributedCharacterIterator} with no attributes. Subclasses
     * that support fields should override this and create an
     * {@code AttributedCharacterIterator} with meaningful attributes.
     *
     * @throws    NullPointerException if obj is null.
     * @throws    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.

 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. 
Params:
  • source – A String, part of which should be parsed.
  • pos – A ParsePosition object with index and error index information as described above.
Throws:
Returns:An Object parsed from the string. In case of error, returns null.
/**
     * Parses text from a string to produce an object.
     * <p>
     * The method attempts to parse text starting at the index given by
     * {@code pos}.
     * If parsing succeeds, then the index of {@code 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 {@code pos} 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} is not
     * changed, the error index of {@code pos} is set to the index of
     * the character where the error occurred, and null is returned.
     *
     * @param source A {@code String}, part of which should be parsed.
     * @param pos A {@code ParsePosition} object with index and error
     *            index information as described above.
     * @return An {@code Object} 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.

Params:
  • source – A String whose beginning should be parsed.
Throws:
Returns:An Object parsed from the string.
/**
     * 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} whose beginning should be parsed.
     * @return An {@code Object} parsed from the string.
     * @throws    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.

Returns:a clone of this instance.
/**
     * 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 AttributedCharacterIterator for the String s. 
Params:
  • s – String to create AttributedCharacterIterator from
Returns:AttributedCharacterIterator wrapping s
/**
     * Creates an {@code AttributedCharacterIterator} for the String
     * {@code s}.
     *
     * @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 AttributedCharacterIterator containing the concatenated contents of the passed in AttributedCharacterIterators. 
Params:
  • iterators – AttributedCharacterIterators used to create resulting
                 AttributedCharacterIterators
Returns:AttributedCharacterIterator wrapping passed in
        AttributedCharacterIterators
/**
     * Creates an {@code AttributedCharacterIterator} containing the
     * concatenated contents of the passed in
     * {@code AttributedCharacterIterator}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 string and additional key/value pair key, value. 
Params:
  • string – String to create AttributedCharacterIterator from
  • key – Key for AttributedCharacterIterator
  • value – Value associated with key in AttributedCharacterIterator
Returns:AttributedCharacterIterator wrapping args
/**
     * Returns an AttributedCharacterIterator with the String
     * {@code string} and additional key/value pair {@code key},
     * {@code value}.
     *
     * @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 iterator and the additional attribute key value. 
Params:
  • iterator – Initial AttributedCharacterIterator to add arg to
  • key – Key for AttributedCharacterIterator
  • value – Value associated with key in AttributedCharacterIterator
Returns:AttributedCharacterIterator wrapping args
/**
     * Creates an AttributedCharacterIterator with the contents of
     * {@code iterator} and the additional attribute {@code key}
     * {@code value}.
     *
     * @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 AttributedCharacterIterator returned from Format.formatToCharacterIterator and as field identifiers in FieldPosition. 
Since:1.4
/**
     * Defines constants that are used as attribute keys in the
     * {@code AttributedCharacterIterator} returned
     * from {@code Format.formatToCharacterIterator} and as
     * field identifiers in {@code FieldPosition}.
     *
     * @since 1.4
     */
    public static class Field extends AttributedCharacterIterator.Attribute {

        // Proclaim serial compatibility with 1.4 FCS
        @java.io.Serial
        private static final long serialVersionUID = 276966692217360283L;

        
Creates a Field with the specified name.

Params:
  • name – Name of the attribute
/**
         * 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 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. 
See Also:
/**
     * FieldDelegate is notified by the various {@code 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 {@code FieldPosition} or for an
     * {@code AttributedCharacterIterator}.
     * <p>
     * Delegates should NOT assume that the {@code Format} 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 attr. 
Params:
  • attr – Identifies the field matched
  • value – Value associated with the field
  • start – Beginning location of the field, will be >= 0
  • end – End of the field, will be >= start and <= buffer.length()
  • buffer – Contains current formatted value, receiver should
       NOT modify it.
/**
         * 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}.
         *
         * @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.

Params:
  • fieldID – Identifies the field by integer
  • attr – Identifies the field matched
  • value – Value associated with the field
  • start – Beginning location of the field, will be >= 0
  • end – End of the field, will be >= start and <= buffer.length()
  • buffer – Contains current formatted value, receiver should
       NOT modify it.
/**
         * 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);
    }
}