https://openjdk.java.net/ 
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 * Copyright (c) 1996, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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/*
 * (C) Copyright Taligent, Inc. 1996 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996 - 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.InvalidObjectException;
import java.text.spi.DateFormatProvider;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;
import java.util.MissingResourceException;
import java.util.ResourceBundle;
import java.util.TimeZone;
import java.util.spi.LocaleServiceProvider;
import sun.util.locale.provider.LocaleProviderAdapter;
import sun.util.locale.provider.LocaleServiceProviderPool;


DateFormat is an abstract class for date/time formatting subclasses which formats and parses dates or time in a language-independent manner. The date/time formatting subclass, such as SimpleDateFormat, allows for formatting (i.e., date → text), parsing (text → date), and normalization. The date is represented as a Date object or
as the milliseconds since January 1, 1970, 00:00:00 GMT.

DateFormat provides many class methods for obtaining default date/time formatters based on the default or a given locale and a number of formatting styles. The formatting styles include FULL, LONG, MEDIUM, and SHORT. More detail and examples of using these styles are provided in the method descriptions. 
DateFormat helps you to format and parse dates for any locale. Your code can be completely independent of the locale conventions for months, days of the week, or even the calendar format: lunar vs. solar. 
To format a date for the current Locale, use one of the
static factory methods:




myString = DateFormat.getDateInstance().format(myDate);





If you are formatting multiple dates, it is
more efficient to get the format and use it multiple times so that
the system doesn't have to fetch the information about the local
language and country conventions multiple times.




DateFormat df = DateFormat.getDateInstance();
for (int i = 0; i < myDate.length; ++i) {
    output.println(df.format(myDate[i]) + "; ");
 }





To format a date for a different Locale, specify it in the call to getDateInstance(). 



DateFormat df = DateFormat.getDateInstance(DateFormat.LONG, Locale.FRANCE);





If the specified locale contains "ca" (calendar), "rg" (region override),
and/or "tz" (timezone) Unicode
extensions, the calendar, the country and/or the time zone for formatting
are overridden. If both "ca" and "rg" are specified, the calendar from the "ca"
extension supersedes the implicit one from the "rg" extension.

You can use a DateFormat to parse also.




myDate = df.parse(myString);





Use getDateInstance to get the normal date format for that country. There are other static factory methods available. Use getTimeInstance to get the time format for that country. Use getDateTimeInstance to get a date and time format. You can pass in different options to these factory methods to control the length of the result; from SHORT to MEDIUM to LONG to FULL. The exact result depends on the locale, but generally: 
  • SHORT is completely numeric, such as 12.13.52 or 3:30pm 
  • MEDIUM is longer, such as Jan 12, 1952 
  • LONG is longer, such as January 12, 1952 or 3:30:32pm 
  • FULL is pretty completely specified, such as Tuesday, April 12, 1952 AD or 3:30:42pm PST. 


You can also set the time zone on the format if you wish. If you want even more control over the format or parsing, (or want to give your users more control), you can try casting the DateFormat you get from the factory methods to a SimpleDateFormat. This will work for the majority of countries; just remember to put it in a try block in case you encounter an unusual one. 
You can also use forms of the parse and format methods with ParsePosition and FieldPosition to allow you to 
  • progressively parse through pieces of a string.

  • align any particular field, or find out where it is for selection
on the screen.



Synchronization



Date 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.

Author:      Mark Davis, Chen-Lieh Huang, Alan Liu
See Also:
Implementation Requirements:

Since:1.1
/**
 * {@code DateFormat} is an abstract class for date/time formatting subclasses which
 * formats and parses dates or time in a language-independent manner.
 * The date/time formatting subclass, such as {@link SimpleDateFormat}, allows for
 * formatting (i.e., date &rarr; text), parsing (text &rarr; date), and
 * normalization.  The date is represented as a <code>Date</code> object or
 * as the milliseconds since January 1, 1970, 00:00:00 GMT.
 *
 * <p>{@code DateFormat} provides many class methods for obtaining default date/time
 * formatters based on the default or a given locale and a number of formatting
 * styles. The formatting styles include {@link #FULL}, {@link #LONG}, {@link #MEDIUM}, and {@link #SHORT}. More
 * detail and examples of using these styles are provided in the method
 * descriptions.
 *
 * <p>{@code DateFormat} helps you to format and parse dates for any locale.
 * Your code can be completely independent of the locale conventions for
 * months, days of the week, or even the calendar format: lunar vs. solar.
 *
 * <p>To format a date for the current Locale, use one of the
 * static factory methods:
 * <blockquote>
 * <pre>{@code
 * myString = DateFormat.getDateInstance().format(myDate);
 * }</pre>
 * </blockquote>
 * <p>If you are formatting multiple dates, it is
 * more efficient to get the format and use it multiple times so that
 * the system doesn't have to fetch the information about the local
 * language and country conventions multiple times.
 * <blockquote>
 * <pre>{@code
 * DateFormat df = DateFormat.getDateInstance();
 * for (int i = 0; i < myDate.length; ++i) {
 *     output.println(df.format(myDate[i]) + "; ");
 * }
 * }</pre>
 * </blockquote>
 * <p>To format a date for a different Locale, specify it in the
 * call to {@link #getDateInstance(int, Locale) getDateInstance()}.
 * <blockquote>
 * <pre>{@code
 * DateFormat df = DateFormat.getDateInstance(DateFormat.LONG, Locale.FRANCE);
 * }</pre>
 * </blockquote>
 *
 * <p>If the specified locale contains "ca" (calendar), "rg" (region override),
 * and/or "tz" (timezone) <a href="../util/Locale.html#def_locale_extension">Unicode
 * extensions</a>, the calendar, the country and/or the time zone for formatting
 * are overridden. If both "ca" and "rg" are specified, the calendar from the "ca"
 * extension supersedes the implicit one from the "rg" extension.
 *
 * <p>You can use a DateFormat to parse also.
 * <blockquote>
 * <pre>{@code
 * myDate = df.parse(myString);
 * }</pre>
 * </blockquote>
 * <p>Use {@code getDateInstance} to get the normal date format for that country.
 * There are other static factory methods available.
 * Use {@code getTimeInstance} to get the time format for that country.
 * Use {@code getDateTimeInstance} to get a date and time format. You can pass in
 * different options to these factory methods to control the length of the
 * result; from {@link #SHORT} to {@link #MEDIUM} to {@link #LONG} to {@link #FULL}. The exact result depends
 * on the locale, but generally:
 * <ul><li>{@link #SHORT} is completely numeric, such as {@code 12.13.52} or {@code 3:30pm}
 * <li>{@link #MEDIUM} is longer, such as {@code Jan 12, 1952}
 * <li>{@link #LONG} is longer, such as {@code January 12, 1952} or {@code 3:30:32pm}
 * <li>{@link #FULL} is pretty completely specified, such as
 * {@code Tuesday, April 12, 1952 AD or 3:30:42pm PST}.
 * </ul>
 *
 * <p>You can also set the time zone on the format if you wish.
 * If you want even more control over the format or parsing,
 * (or want to give your users more control),
 * you can try casting the {@code DateFormat} you get from the factory methods
 * to a {@link SimpleDateFormat}. This will work for the majority
 * of countries; just remember to put it in a {@code try} block in case you
 * encounter an unusual one.
 *
 * <p>You can also use forms of the parse and format methods with
 * {@link ParsePosition} and {@link FieldPosition} to
 * allow you to
 * <ul><li>progressively parse through pieces of a string.
 * <li>align any particular field, or find out where it is for selection
 * on the screen.
 * </ul>
 *
 * <h3><a id="synchronization">Synchronization</a></h3>
 *
 * <p>
 * Date 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.
 *
 * @implSpec
 * <ul><li>The {@link #format(Date, StringBuffer, FieldPosition)} and
 * {@link #parse(String, ParsePosition)} methods may throw
 * {@code NullPointerException}, if any of their parameter is {@code null}.
 * The subclass may provide its own implementation and specification about
 * {@code NullPointerException}.</li>
 * <li>The {@link #setCalendar(Calendar)}, {@link
 * #setNumberFormat(NumberFormat)} and {@link #setTimeZone(TimeZone)} methods
 * do not throw {@code NullPointerException} when their parameter is
 * {@code null}, but any subsequent operations on the same instance may throw
 * {@code NullPointerException}.</li>
 * <li>The {@link #getCalendar()}, {@link #getNumberFormat()} and
 * {@link getTimeZone()} methods may return {@code null}, if the respective
 * values of this instance is set to {@code null} through the corresponding
 * setter methods. For Example: {@link #getTimeZone()} may return {@code null},
 * if the {@code TimeZone} value of this instance is set as
 * {@link #setTimeZone(java.util.TimeZone) setTimeZone(null)}.</li>
 * </ul>
 *
 * @see          Format
 * @see          NumberFormat
 * @see          SimpleDateFormat
 * @see          java.util.Calendar
 * @see          java.util.GregorianCalendar
 * @see          java.util.TimeZone
 * @author       Mark Davis, Chen-Lieh Huang, Alan Liu
 * @since 1.1
 */
public abstract class DateFormat extends Format {

    
The Calendar instance used for calculating the date-time fields and the instant of time. This field is used for both formatting and parsing. 
Subclasses should initialize this field to a Calendar appropriate for the Locale associated with this DateFormat.

@serial
/**
     * The {@link Calendar} instance used for calculating the date-time fields
     * and the instant of time. This field is used for both formatting and
     * parsing.
     *
     * <p>Subclasses should initialize this field to a {@link Calendar}
     * appropriate for the {@link Locale} associated with this
     * <code>DateFormat</code>.
     * @serial
     */
    protected Calendar calendar;

    
The number formatter that DateFormat uses to format numbers
in dates and times.  Subclasses should initialize this to a number format
appropriate for the locale associated with this DateFormat.

@serial
/**
     * The number formatter that <code>DateFormat</code> uses to format numbers
     * in dates and times.  Subclasses should initialize this to a number format
     * appropriate for the locale associated with this <code>DateFormat</code>.
     * @serial
     */
    protected NumberFormat numberFormat;

    
Useful constant for ERA field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for ERA field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int ERA_FIELD = 0;
    
Useful constant for YEAR field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for YEAR field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int YEAR_FIELD = 1;
    
Useful constant for MONTH field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for MONTH field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int MONTH_FIELD = 2;
    
Useful constant for DATE field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for DATE field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int DATE_FIELD = 3;
    
Useful constant for one-based HOUR_OF_DAY field alignment.
Used in FieldPosition of date/time formatting.
HOUR_OF_DAY1_FIELD is used for the one-based 24-hour clock.
For example, 23:59 + 01:00 results in 24:59.

/**
     * Useful constant for one-based HOUR_OF_DAY field alignment.
     * Used in FieldPosition of date/time formatting.
     * HOUR_OF_DAY1_FIELD is used for the one-based 24-hour clock.
     * For example, 23:59 + 01:00 results in 24:59.
     */
    public static final int HOUR_OF_DAY1_FIELD = 4;
    
Useful constant for zero-based HOUR_OF_DAY field alignment.
Used in FieldPosition of date/time formatting.
HOUR_OF_DAY0_FIELD is used for the zero-based 24-hour clock.
For example, 23:59 + 01:00 results in 00:59.

/**
     * Useful constant for zero-based HOUR_OF_DAY field alignment.
     * Used in FieldPosition of date/time formatting.
     * HOUR_OF_DAY0_FIELD is used for the zero-based 24-hour clock.
     * For example, 23:59 + 01:00 results in 00:59.
     */
    public static final int HOUR_OF_DAY0_FIELD = 5;
    
Useful constant for MINUTE field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for MINUTE field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int MINUTE_FIELD = 6;
    
Useful constant for SECOND field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for SECOND field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int SECOND_FIELD = 7;
    
Useful constant for MILLISECOND field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for MILLISECOND field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int MILLISECOND_FIELD = 8;
    
Useful constant for DAY_OF_WEEK field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for DAY_OF_WEEK field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int DAY_OF_WEEK_FIELD = 9;
    
Useful constant for DAY_OF_YEAR field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for DAY_OF_YEAR field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int DAY_OF_YEAR_FIELD = 10;
    
Useful constant for DAY_OF_WEEK_IN_MONTH field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for DAY_OF_WEEK_IN_MONTH field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int DAY_OF_WEEK_IN_MONTH_FIELD = 11;
    
Useful constant for WEEK_OF_YEAR field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for WEEK_OF_YEAR field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int WEEK_OF_YEAR_FIELD = 12;
    
Useful constant for WEEK_OF_MONTH field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for WEEK_OF_MONTH field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int WEEK_OF_MONTH_FIELD = 13;
    
Useful constant for AM_PM field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for AM_PM field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int AM_PM_FIELD = 14;
    
Useful constant for one-based HOUR field alignment.
Used in FieldPosition of date/time formatting.
HOUR1_FIELD is used for the one-based 12-hour clock.
For example, 11:30 PM + 1 hour results in 12:30 AM.

/**
     * Useful constant for one-based HOUR field alignment.
     * Used in FieldPosition of date/time formatting.
     * HOUR1_FIELD is used for the one-based 12-hour clock.
     * For example, 11:30 PM + 1 hour results in 12:30 AM.
     */
    public static final int HOUR1_FIELD = 15;
    
Useful constant for zero-based HOUR field alignment.
Used in FieldPosition of date/time formatting.
HOUR0_FIELD is used for the zero-based 12-hour clock.
For example, 11:30 PM + 1 hour results in 00:30 AM.

/**
     * Useful constant for zero-based HOUR field alignment.
     * Used in FieldPosition of date/time formatting.
     * HOUR0_FIELD is used for the zero-based 12-hour clock.
     * For example, 11:30 PM + 1 hour results in 00:30 AM.
     */
    public static final int HOUR0_FIELD = 16;
    
Useful constant for TIMEZONE field alignment.
Used in FieldPosition of date/time formatting.

/**
     * Useful constant for TIMEZONE field alignment.
     * Used in FieldPosition of date/time formatting.
     */
    public static final int TIMEZONE_FIELD = 17;

    // Proclaim serial compatibility with 1.1 FCS
    private static final long serialVersionUID = 7218322306649953788L;

    
Formats the given Object into a date-time string. The formatted string is appended to the given StringBuffer. 
Params:
  • obj – Must be a Date or a Number representing a millisecond offset from the Epoch.
  • toAppendTo – The string buffer for the returning date-time string.
  • fieldPosition – keeps track on the position of the field within the returned string. For example, given a date-time text "1996.07.10 AD at 15:08:56 PDT", if the given fieldPosition is YEAR_FIELD, the begin index and end index of fieldPosition will be set to 0 and 4, respectively. Notice that if the same date-time field appears more than once in a pattern, the fieldPosition will be set for the first occurrence of that date-time field. For instance, formatting a Date to the date-time string "1 PM PDT (Pacific Daylight Time)" using the pattern "h a z (zzzz)" and the alignment field TIMEZONE_FIELD, the begin index and end index of fieldPosition will be set to 5 and 8, respectively, for the first occurrence of the timezone pattern character 'z'.
Throws:
See Also:
Returns:the string buffer passed in as toAppendTo, with formatted text appended.
/**
     * Formats the given {@code Object} into a date-time string. The formatted
     * string is appended to the given {@code StringBuffer}.
     *
     * @param obj Must be a {@code Date} or a {@code Number} representing a
     * millisecond offset from the <a href="../util/Calendar.html#Epoch">Epoch</a>.
     * @param toAppendTo The string buffer for the returning date-time string.
     * @param fieldPosition keeps track on the position of the field within
     * the returned string. For example, given a date-time text
     * {@code "1996.07.10 AD at 15:08:56 PDT"}, if the given {@code fieldPosition}
     * is {@link DateFormat#YEAR_FIELD}, the begin index and end index of
     * {@code fieldPosition} will be set to 0 and 4, respectively.
     * Notice that if the same date-time field appears more than once in a
     * pattern, the {@code fieldPosition} will be set for the first occurrence
     * of that date-time field. For instance, formatting a {@code Date} to the
     * date-time string {@code "1 PM PDT (Pacific Daylight Time)"} using the
     * pattern {@code "h a z (zzzz)"} and the alignment field
     * {@link DateFormat#TIMEZONE_FIELD}, the begin index and end index of
     * {@code fieldPosition} will be set to 5 and 8, respectively, for the
     * first occurrence of the timezone pattern character {@code 'z'}.
     * @return the string buffer passed in as {@code toAppendTo},
     *         with formatted text appended.
     * @exception IllegalArgumentException if the {@code Format} cannot format
     *            the given {@code obj}.
     * @see java.text.Format
     */
    public final StringBuffer format(Object obj, StringBuffer toAppendTo,
                                     FieldPosition fieldPosition)
    {
        if (obj instanceof Date)
            return format( (Date)obj, toAppendTo, fieldPosition );
        else if (obj instanceof Number)
            return format( new Date(((Number)obj).longValue()),
                          toAppendTo, fieldPosition );
        else
            throw new IllegalArgumentException("Cannot format given Object as a Date");
    }

    
Formats a Date into a date-time string. The formatted string is appended to the given StringBuffer. 
Params:
  • date – a Date to be formatted into a date-time string.
  • toAppendTo – the string buffer for the returning date-time string.
  • fieldPosition – keeps track on the position of the field within the returned string. For example, given a date-time text "1996.07.10 AD at 15:08:56 PDT", if the given fieldPosition is YEAR_FIELD, the begin index and end index of fieldPosition will be set to 0 and 4, respectively. Notice that if the same date-time field appears more than once in a pattern, the fieldPosition will be set for the first occurrence of that date-time field. For instance, formatting a Date to the date-time string "1 PM PDT (Pacific Daylight Time)" using the pattern "h a z (zzzz)" and the alignment field TIMEZONE_FIELD, the begin index and end index of fieldPosition will be set to 5 and 8, respectively, for the first occurrence of the timezone pattern character 'z'.
Returns:the string buffer passed in as toAppendTo, with formatted text appended.
/**
     * Formats a {@link Date} into a date-time string. The formatted
     * string is appended to the given {@code StringBuffer}.
     *
     * @param date a Date to be formatted into a date-time string.
     * @param toAppendTo the string buffer for the returning date-time string.
     * @param fieldPosition keeps track on the position of the field within
     * the returned string. For example, given a date-time text
     * {@code "1996.07.10 AD at 15:08:56 PDT"}, if the given {@code fieldPosition}
     * is {@link DateFormat#YEAR_FIELD}, the begin index and end index of
     * {@code fieldPosition} will be set to 0 and 4, respectively.
     * Notice that if the same date-time field appears more than once in a
     * pattern, the {@code fieldPosition} will be set for the first occurrence
     * of that date-time field. For instance, formatting a {@code Date} to the
     * date-time string {@code "1 PM PDT (Pacific Daylight Time)"} using the
     * pattern {@code "h a z (zzzz)"} and the alignment field
     * {@link DateFormat#TIMEZONE_FIELD}, the begin index and end index of
     * {@code fieldPosition} will be set to 5 and 8, respectively, for the
     * first occurrence of the timezone pattern character {@code 'z'}.
     * @return the string buffer passed in as {@code toAppendTo}, with formatted
     * text appended.
     */
    public abstract StringBuffer format(Date date, StringBuffer toAppendTo,
                                        FieldPosition fieldPosition);

    
Formats a Date into a date-time string. 
Params:
  • date – the time value to be formatted into a date-time string.
Returns:the formatted date-time string.
/**
      * Formats a {@link Date} into a date-time string.
      *
      * @param date the time value to be formatted into a date-time string.
      * @return the formatted date-time string.
     */
    public final String format(Date date)
    {
        return format(date, new StringBuffer(),
                      DontCareFieldPosition.INSTANCE).toString();
    }

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

 See the parse(String, ParsePosition) method for more information on date parsing. 
Params:
  • source – A String whose beginning should be parsed.
Throws:
  • ParseException – if the beginning of the specified string
           cannot be parsed.
Returns:A Date parsed from the string.
/**
     * Parses text from the beginning of the given string to produce a date.
     * The method may not use the entire text of the given string.
     * <p>
     * See the {@link #parse(String, ParsePosition)} method for more information
     * on date parsing.
     *
     * @param source A <code>String</code> whose beginning should be parsed.
     * @return A <code>Date</code> parsed from the string.
     * @exception ParseException if the beginning of the specified string
     *            cannot be parsed.
     */
    public Date parse(String source) throws ParseException
    {
        ParsePosition pos = new ParsePosition(0);
        Date result = parse(source, pos);
        if (pos.index == 0)
            throw new ParseException("Unparseable date: \"" + source + "\"" ,
                pos.errorIndex);
        return result;
    }

    
Parse a date/time string according to the given parse position. For example, a time text "07/10/96 4:5 PM, PDT" will be parsed into a Date that is equivalent to Date(837039900000L). 
 By default, parsing is lenient: If the input is not in the form used by this object's format method but can still be parsed as a date, then the parse succeeds. Clients may insist on strict adherence to the format by calling setLenient(false). 
This parsing operation uses the calendar to produce a Date. As a result, the calendar's date-time fields and the TimeZone value may have been overwritten, depending on subclass implementations. Any 
TimeZone value that has previously been set by a call to setTimeZone may need to be restored for further operations. 
Params:
  • source –  The date/time string to be parsed
  • pos –   On input, the position at which to start parsing; on
             output, the position at which parsing terminated, or the
             start position if the parse failed.
Returns: A Date, or null if the input could not be parsed
/**
     * Parse a date/time string according to the given parse position.  For
     * example, a time text {@code "07/10/96 4:5 PM, PDT"} will be parsed into a {@code Date}
     * that is equivalent to {@code Date(837039900000L)}.
     *
     * <p> By default, parsing is lenient: If the input is not in the form used
     * by this object's format method but can still be parsed as a date, then
     * the parse succeeds.  Clients may insist on strict adherence to the
     * format by calling {@link #setLenient(boolean) setLenient(false)}.
     *
     * <p>This parsing operation uses the {@link #calendar} to produce
     * a {@code Date}. As a result, the {@code calendar}'s date-time
     * fields and the {@code TimeZone} value may have been
     * overwritten, depending on subclass implementations. Any {@code
     * TimeZone} value that has previously been set by a call to
     * {@link #setTimeZone(java.util.TimeZone) setTimeZone} may need
     * to be restored for further operations.
     *
     * @param source  The date/time string to be parsed
     *
     * @param pos   On input, the position at which to start parsing; on
     *              output, the position at which parsing terminated, or the
     *              start position if the parse failed.
     *
     * @return      A {@code Date}, or {@code null} if the input could not be parsed
     */
    public abstract Date parse(String source, ParsePosition pos);

    
Parses text from a string to produce a Date.


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
date 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 date parsing. 
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:A Date parsed from the string. In case of
        error, returns null.
/**
     * Parses text from a string to produce a <code>Date</code>.
     * <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
     * date 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.
     * <p>
     * See the {@link #parse(String, ParsePosition)} method for more information
     * on date parsing.
     *
     * @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 A <code>Date</code> parsed from the string. In case of
     *         error, returns null.
     * @throws NullPointerException if {@code source} or {@code pos} is null.
     */
    public Object parseObject(String source, ParsePosition pos) {
        return parse(source, pos);
    }

    
Constant for full style pattern.

/**
     * Constant for full style pattern.
     */
    public static final int FULL = 0;
    
Constant for long style pattern.

/**
     * Constant for long style pattern.
     */
    public static final int LONG = 1;
    
Constant for medium style pattern.

/**
     * Constant for medium style pattern.
     */
    public static final int MEDIUM = 2;
    
Constant for short style pattern.

/**
     * Constant for short style pattern.
     */
    public static final int SHORT = 3;
    
Constant for default style pattern.  Its value is MEDIUM.

/**
     * Constant for default style pattern.  Its value is MEDIUM.
     */
    public static final int DEFAULT = MEDIUM;

    
Gets the time formatter with the default formatting style for the default FORMAT locale. 
This is equivalent to calling getTimeInstance(DEFAULT,
    Locale.getDefault(Locale.Category.FORMAT)). 
See Also:
Returns:a time formatter.
/**
     * Gets the time formatter with the default formatting style
     * for the default {@link java.util.Locale.Category#FORMAT FORMAT} locale.
     * <p>This is equivalent to calling
     * {@link #getTimeInstance(int, Locale) getTimeInstance(DEFAULT,
     *     Locale.getDefault(Locale.Category.FORMAT))}.
     * @see java.util.Locale#getDefault(java.util.Locale.Category)
     * @see java.util.Locale.Category#FORMAT
     * @return a time formatter.
     */
    public static final DateFormat getTimeInstance()
    {
        return get(DEFAULT, 0, 1, Locale.getDefault(Locale.Category.FORMAT));
    }

    
Gets the time formatter with the given formatting style for the default FORMAT locale. 
This is equivalent to calling getTimeInstance(style,
    Locale.getDefault(Locale.Category.FORMAT)). 
Params:
  • style – the given formatting style. For example,
SHORT for "h:mm a" in the US locale.
See Also:
Returns:a time formatter.
/**
     * Gets the time formatter with the given formatting style
     * for the default {@link java.util.Locale.Category#FORMAT FORMAT} locale.
     * <p>This is equivalent to calling
     * {@link #getTimeInstance(int, Locale) getTimeInstance(style,
     *     Locale.getDefault(Locale.Category.FORMAT))}.
     * @see java.util.Locale#getDefault(java.util.Locale.Category)
     * @see java.util.Locale.Category#FORMAT
     * @param style the given formatting style. For example,
     * SHORT for "h:mm a" in the US locale.
     * @return a time formatter.
     */
    public static final DateFormat getTimeInstance(int style)
    {
        return get(style, 0, 1, Locale.getDefault(Locale.Category.FORMAT));
    }

    
Gets the time formatter with the given formatting style
for the given locale.

Params:
  • style – the given formatting style. For example,
SHORT for "h:mm a" in the US locale.
  • aLocale – the given locale.
Returns:a time formatter.
/**
     * Gets the time formatter with the given formatting style
     * for the given locale.
     * @param style the given formatting style. For example,
     * SHORT for "h:mm a" in the US locale.
     * @param aLocale the given locale.
     * @return a time formatter.
     */
    public static final DateFormat getTimeInstance(int style,
                                                 Locale aLocale)
    {
        return get(style, 0, 1, aLocale);
    }

    
Gets the date formatter with the default formatting style for the default FORMAT locale. 
This is equivalent to calling getDateInstance(DEFAULT,
    Locale.getDefault(Locale.Category.FORMAT)). 
See Also:
Returns:a date formatter.
/**
     * Gets the date formatter with the default formatting style
     * for the default {@link java.util.Locale.Category#FORMAT FORMAT} locale.
     * <p>This is equivalent to calling
     * {@link #getDateInstance(int, Locale) getDateInstance(DEFAULT,
     *     Locale.getDefault(Locale.Category.FORMAT))}.
     * @see java.util.Locale#getDefault(java.util.Locale.Category)
     * @see java.util.Locale.Category#FORMAT
     * @return a date formatter.
     */
    public static final DateFormat getDateInstance()
    {
        return get(0, DEFAULT, 2, Locale.getDefault(Locale.Category.FORMAT));
    }

    
Gets the date formatter with the given formatting style for the default FORMAT locale. 
This is equivalent to calling getDateInstance(style,
    Locale.getDefault(Locale.Category.FORMAT)). 
Params:
  • style – the given formatting style. For example,
SHORT for "M/d/yy" in the US locale.
See Also:
Returns:a date formatter.
/**
     * Gets the date formatter with the given formatting style
     * for the default {@link java.util.Locale.Category#FORMAT FORMAT} locale.
     * <p>This is equivalent to calling
     * {@link #getDateInstance(int, Locale) getDateInstance(style,
     *     Locale.getDefault(Locale.Category.FORMAT))}.
     * @see java.util.Locale#getDefault(java.util.Locale.Category)
     * @see java.util.Locale.Category#FORMAT
     * @param style the given formatting style. For example,
     * SHORT for "M/d/yy" in the US locale.
     * @return a date formatter.
     */
    public static final DateFormat getDateInstance(int style)
    {
        return get(0, style, 2, Locale.getDefault(Locale.Category.FORMAT));
    }

    
Gets the date formatter with the given formatting style
for the given locale.

Params:
  • style – the given formatting style. For example,
SHORT for "M/d/yy" in the US locale.
  • aLocale – the given locale.
Returns:a date formatter.
/**
     * Gets the date formatter with the given formatting style
     * for the given locale.
     * @param style the given formatting style. For example,
     * SHORT for "M/d/yy" in the US locale.
     * @param aLocale the given locale.
     * @return a date formatter.
     */
    public static final DateFormat getDateInstance(int style,
                                                 Locale aLocale)
    {
        return get(0, style, 2, aLocale);
    }

    
Gets the date/time formatter with the default formatting style for the default FORMAT locale. 
This is equivalent to calling getDateTimeInstance(DEFAULT,
    DEFAULT, Locale.getDefault(Locale.Category.FORMAT)). 
See Also:
Returns:a date/time formatter.
/**
     * Gets the date/time formatter with the default formatting style
     * for the default {@link java.util.Locale.Category#FORMAT FORMAT} locale.
     * <p>This is equivalent to calling
     * {@link #getDateTimeInstance(int, int, Locale) getDateTimeInstance(DEFAULT,
     *     DEFAULT, Locale.getDefault(Locale.Category.FORMAT))}.
     * @see java.util.Locale#getDefault(java.util.Locale.Category)
     * @see java.util.Locale.Category#FORMAT
     * @return a date/time formatter.
     */
    public static final DateFormat getDateTimeInstance()
    {
        return get(DEFAULT, DEFAULT, 3, Locale.getDefault(Locale.Category.FORMAT));
    }

    
Gets the date/time formatter with the given date and time formatting styles for the default FORMAT locale. 
This is equivalent to calling getDateTimeInstance(dateStyle,
    timeStyle, Locale.getDefault(Locale.Category.FORMAT)). 
Params:
  • dateStyle – the given date formatting style. For example,
SHORT for "M/d/yy" in the US locale.
  • timeStyle – the given time formatting style. For example,
SHORT for "h:mm a" in the US locale.
See Also:
Returns:a date/time formatter.
/**
     * Gets the date/time formatter with the given date and time
     * formatting styles for the default {@link java.util.Locale.Category#FORMAT FORMAT} locale.
     * <p>This is equivalent to calling
     * {@link #getDateTimeInstance(int, int, Locale) getDateTimeInstance(dateStyle,
     *     timeStyle, Locale.getDefault(Locale.Category.FORMAT))}.
     * @see java.util.Locale#getDefault(java.util.Locale.Category)
     * @see java.util.Locale.Category#FORMAT
     * @param dateStyle the given date formatting style. For example,
     * SHORT for "M/d/yy" in the US locale.
     * @param timeStyle the given time formatting style. For example,
     * SHORT for "h:mm a" in the US locale.
     * @return a date/time formatter.
     */
    public static final DateFormat getDateTimeInstance(int dateStyle,
                                                       int timeStyle)
    {
        return get(timeStyle, dateStyle, 3, Locale.getDefault(Locale.Category.FORMAT));
    }

    
Gets the date/time formatter with the given formatting styles
for the given locale.

Params:
  • dateStyle – the given date formatting style.
  • timeStyle – the given time formatting style.
  • aLocale – the given locale.
Returns:a date/time formatter.
/**
     * Gets the date/time formatter with the given formatting styles
     * for the given locale.
     * @param dateStyle the given date formatting style.
     * @param timeStyle the given time formatting style.
     * @param aLocale the given locale.
     * @return a date/time formatter.
     */
    public static final DateFormat
        getDateTimeInstance(int dateStyle, int timeStyle, Locale aLocale)
    {
        return get(timeStyle, dateStyle, 3, aLocale);
    }

    
Get a default date/time formatter that uses the SHORT style for both the
date and the time.

Returns:a date/time formatter
/**
     * Get a default date/time formatter that uses the SHORT style for both the
     * date and the time.
     *
     * @return a date/time formatter
     */
    public static final DateFormat getInstance() {
        return getDateTimeInstance(SHORT, SHORT);
    }

    
Returns an array of all locales for which the
get*Instance methods of this class can return localized instances. The returned array represents the union of locales supported by the Java runtime and by installed DateFormatProvider implementations. It must contain at least a Locale instance equal to Locale.US. 
Returns:An array of locales for which localized
        DateFormat instances are available.
/**
     * Returns an array of all locales for which the
     * <code>get*Instance</code> methods of this class can return
     * localized instances.
     * The returned array represents the union of locales supported by the Java
     * runtime and by installed
     * {@link java.text.spi.DateFormatProvider DateFormatProvider} implementations.
     * It must contain at least a <code>Locale</code> instance equal to
     * {@link java.util.Locale#US Locale.US}.
     *
     * @return An array of locales for which localized
     *         <code>DateFormat</code> instances are available.
     */
    public static Locale[] getAvailableLocales()
    {
        LocaleServiceProviderPool pool =
            LocaleServiceProviderPool.getPool(DateFormatProvider.class);
        return pool.getAvailableLocales();
    }

    
Set the calendar to be used by this date format.  Initially, the default
calendar for the specified or default locale is used.

Any TimeZone and leniency values that have previously been set are overwritten by newCalendar's values. 
Params:
  • newCalendar – the new Calendar to be used by the date format
/**
     * Set the calendar to be used by this date format.  Initially, the default
     * calendar for the specified or default locale is used.
     *
     * <p>Any {@link java.util.TimeZone TimeZone} and {@linkplain
     * #isLenient() leniency} values that have previously been set are
     * overwritten by {@code newCalendar}'s values.
     *
     * @param newCalendar the new {@code Calendar} to be used by the date format
     */
    public void setCalendar(Calendar newCalendar)
    {
        this.calendar = newCalendar;
    }

    
Gets the calendar associated with this date/time formatter.

Returns:the calendar associated with this date/time formatter.
/**
     * Gets the calendar associated with this date/time formatter.
     *
     * @return the calendar associated with this date/time formatter.
     */
    public Calendar getCalendar()
    {
        return calendar;
    }

    
Allows you to set the number formatter.

Params:
  • newNumberFormat – the given new NumberFormat.
/**
     * Allows you to set the number formatter.
     * @param newNumberFormat the given new NumberFormat.
     */
    public void setNumberFormat(NumberFormat newNumberFormat)
    {
        this.numberFormat = newNumberFormat;
    }

    
Gets the number formatter which this date/time formatter uses to
format and parse a time.

Returns:the number formatter which this date/time formatter uses.
/**
     * Gets the number formatter which this date/time formatter uses to
     * format and parse a time.
     * @return the number formatter which this date/time formatter uses.
     */
    public NumberFormat getNumberFormat()
    {
        return numberFormat;
    }

    
Sets the time zone for the calendar of this DateFormat object. This method is equivalent to the following call. 

getCalendar().setTimeZone(zone)



The TimeZone set by this method is overwritten by a setCalendar call. 
The TimeZone set by this method may be overwritten as a result of a call to the parse method. 
Params:
  • zone – the given new time zone.
/**
     * Sets the time zone for the calendar of this {@code DateFormat} object.
     * This method is equivalent to the following call.
     * <blockquote><pre>{@code
     * getCalendar().setTimeZone(zone)
     * }</pre></blockquote>
     *
     * <p>The {@code TimeZone} set by this method is overwritten by a
     * {@link #setCalendar(java.util.Calendar) setCalendar} call.
     *
     * <p>The {@code TimeZone} set by this method may be overwritten as
     * a result of a call to the parse method.
     *
     * @param zone the given new time zone.
     */
    public void setTimeZone(TimeZone zone)
    {
        calendar.setTimeZone(zone);
    }

    
Gets the time zone.
This method is equivalent to the following call.


getCalendar().getTimeZone()



Returns:the time zone associated with the calendar of DateFormat.
/**
     * Gets the time zone.
     * This method is equivalent to the following call.
     * <blockquote><pre>{@code
     * getCalendar().getTimeZone()
     * }</pre></blockquote>
     *
     * @return the time zone associated with the calendar of DateFormat.
     */
    public TimeZone getTimeZone()
    {
        return calendar.getTimeZone();
    }

    
Specify whether or not date/time parsing is to be lenient.  With
lenient parsing, the parser may use heuristics to interpret inputs that
do not precisely match this object's format.  With strict parsing,
inputs must match this object's format.

This method is equivalent to the following call.


getCalendar().setLenient(lenient)



This leniency value is overwritten by a call to setCalendar(). 
Params:
  • lenient – when true, parsing is lenient
See Also:
/**
     * Specify whether or not date/time parsing is to be lenient.  With
     * lenient parsing, the parser may use heuristics to interpret inputs that
     * do not precisely match this object's format.  With strict parsing,
     * inputs must match this object's format.
     *
     * <p>This method is equivalent to the following call.
     * <blockquote><pre>{@code
     * getCalendar().setLenient(lenient)
     * }</pre></blockquote>
     *
     * <p>This leniency value is overwritten by a call to {@link
     * #setCalendar(java.util.Calendar) setCalendar()}.
     *
     * @param lenient when {@code true}, parsing is lenient
     * @see java.util.Calendar#setLenient(boolean)
     */
    public void setLenient(boolean lenient)
    {
        calendar.setLenient(lenient);
    }

    
Tell whether date/time parsing is to be lenient.
This method is equivalent to the following call.


getCalendar().isLenient()



See Also:
Returns:true if the calendar is lenient; false otherwise.
/**
     * Tell whether date/time parsing is to be lenient.
     * This method is equivalent to the following call.
     * <blockquote><pre>{@code
     * getCalendar().isLenient()
     * }</pre></blockquote>
     *
     * @return {@code true} if the {@link #calendar} is lenient;
     *         {@code false} otherwise.
     * @see java.util.Calendar#isLenient()
     */
    public boolean isLenient()
    {
        return calendar.isLenient();
    }

    
Overrides hashCode

/**
     * Overrides hashCode
     */
    public int hashCode() {
        return numberFormat.hashCode();
        // just enough fields for a reasonable distribution
    }

    
Overrides equals

/**
     * Overrides equals
     */
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        DateFormat other = (DateFormat) obj;
        return (// calendar.equivalentTo(other.calendar) // THIS API DOESN'T EXIST YET!
                calendar.getFirstDayOfWeek() == other.calendar.getFirstDayOfWeek() &&
                calendar.getMinimalDaysInFirstWeek() == other.calendar.getMinimalDaysInFirstWeek() &&
                calendar.isLenient() == other.calendar.isLenient() &&
                calendar.getTimeZone().equals(other.calendar.getTimeZone()) &&
                numberFormat.equals(other.numberFormat));
    }

    
Overrides Cloneable

/**
     * Overrides Cloneable
     */
    public Object clone()
    {
        DateFormat other = (DateFormat) super.clone();
        other.calendar = (Calendar) calendar.clone();
        other.numberFormat = (NumberFormat) numberFormat.clone();
        return other;
    }

    
Creates a DateFormat with the given time and/or date style in the given
locale.

Params:
  • timeStyle – a value from 0 to 3 indicating the time format,
ignored if flags is 2
  • dateStyle – a value from 0 to 3 indicating the time format,
ignored if flags is 1
  • flags – either 1 for a time format, 2 for a date format,
or 3 for a date/time format
  • loc – the locale for the format
/**
     * Creates a DateFormat with the given time and/or date style in the given
     * locale.
     * @param timeStyle a value from 0 to 3 indicating the time format,
     * ignored if flags is 2
     * @param dateStyle a value from 0 to 3 indicating the time format,
     * ignored if flags is 1
     * @param flags either 1 for a time format, 2 for a date format,
     * or 3 for a date/time format
     * @param loc the locale for the format
     */
    private static DateFormat get(int timeStyle, int dateStyle,
                                  int flags, Locale loc) {
        if ((flags & 1) != 0) {
            if (timeStyle < 0 || timeStyle > 3) {
                throw new IllegalArgumentException("Illegal time style " + timeStyle);
            }
        } else {
            timeStyle = -1;
        }
        if ((flags & 2) != 0) {
            if (dateStyle < 0 || dateStyle > 3) {
                throw new IllegalArgumentException("Illegal date style " + dateStyle);
            }
        } else {
            dateStyle = -1;
        }

        LocaleProviderAdapter adapter = LocaleProviderAdapter.getAdapter(DateFormatProvider.class, loc);
        DateFormat dateFormat = get(adapter, timeStyle, dateStyle, loc);
        if (dateFormat == null) {
            dateFormat = get(LocaleProviderAdapter.forJRE(), timeStyle, dateStyle, loc);
        }
        return dateFormat;
    }

    private static DateFormat get(LocaleProviderAdapter adapter, int timeStyle, int dateStyle, Locale loc) {
        DateFormatProvider provider = adapter.getDateFormatProvider();
        DateFormat dateFormat;
        if (timeStyle == -1) {
            dateFormat = provider.getDateInstance(dateStyle, loc);
        } else {
            if (dateStyle == -1) {
                dateFormat = provider.getTimeInstance(timeStyle, loc);
            } else {
                dateFormat = provider.getDateTimeInstance(dateStyle, timeStyle, loc);
            }
        }
        return dateFormat;
    }

    
Create a new date format.

/**
     * Create a new date format.
     */
    protected DateFormat() {}

    
Defines constants that are used as attribute keys in the
AttributedCharacterIterator returned
from DateFormat.formatToCharacterIterator and as
field identifiers in FieldPosition.


The class also provides two methods to map
between its constants and the corresponding Calendar constants.

See Also:
Since:1.4
/**
     * Defines constants that are used as attribute keys in the
     * <code>AttributedCharacterIterator</code> returned
     * from <code>DateFormat.formatToCharacterIterator</code> and as
     * field identifiers in <code>FieldPosition</code>.
     * <p>
     * The class also provides two methods to map
     * between its constants and the corresponding Calendar constants.
     *
     * @since 1.4
     * @see java.util.Calendar
     */
    public static class Field extends Format.Field {

        // Proclaim serial compatibility with 1.4 FCS
        private static final long serialVersionUID = 7441350119349544720L;

        // table of all instances in this class, used by readResolve
        private static final Map<String, Field> instanceMap = new HashMap<>(18);
        // Maps from Calendar constant (such as Calendar.ERA) to Field
        // constant (such as Field.ERA).
        private static final Field[] calendarToFieldMapping =
                                             new Field[Calendar.FIELD_COUNT];

        
Calendar field. 
/** Calendar field. */
        private int calendarField;

        
Returns the Field constant that corresponds to
the Calendar constant calendarField.
If there is no direct mapping between the Calendar
constant and a Field, null is returned.

Params:
  • calendarField – Calendar field constant
Throws:
  • IllegalArgumentException – if calendarField is
        not the value of a Calendar field constant.
See Also:
Returns:Field instance representing calendarField.
/**
         * Returns the <code>Field</code> constant that corresponds to
         * the <code>Calendar</code> constant <code>calendarField</code>.
         * If there is no direct mapping between the <code>Calendar</code>
         * constant and a <code>Field</code>, null is returned.
         *
         * @throws IllegalArgumentException if <code>calendarField</code> is
         *         not the value of a <code>Calendar</code> field constant.
         * @param calendarField Calendar field constant
         * @return Field instance representing calendarField.
         * @see java.util.Calendar
         */
        public static Field ofCalendarField(int calendarField) {
            if (calendarField < 0 || calendarField >=
                        calendarToFieldMapping.length) {
                throw new IllegalArgumentException("Unknown Calendar constant "
                                                   + calendarField);
            }
            return calendarToFieldMapping[calendarField];
        }

        
Creates a Field.

Params:
  • name – the name of the Field
  • calendarField – the Calendar constant this
       Field corresponds to; any value, even one
       outside the range of legal Calendar values may
       be used, but -1 should be used for values
       that don't correspond to legal Calendar values
/**
         * Creates a <code>Field</code>.
         *
         * @param name the name of the <code>Field</code>
         * @param calendarField the <code>Calendar</code> constant this
         *        <code>Field</code> corresponds to; any value, even one
         *        outside the range of legal <code>Calendar</code> values may
         *        be used, but <code>-1</code> should be used for values
         *        that don't correspond to legal <code>Calendar</code> values
         */
        protected Field(String name, int calendarField) {
            super(name);
            this.calendarField = calendarField;
            if (this.getClass() == DateFormat.Field.class) {
                instanceMap.put(name, this);
                if (calendarField >= 0) {
                    // assert(calendarField < Calendar.FIELD_COUNT);
                    calendarToFieldMapping[calendarField] = this;
                }
            }
        }

        
Returns the Calendar field associated with this
attribute. For example, if this represents the hours field of
a Calendar, this would return
Calendar.HOUR. If there is no corresponding
Calendar constant, this will return -1.

See Also:
Returns:Calendar constant for this field
/**
         * Returns the <code>Calendar</code> field associated with this
         * attribute. For example, if this represents the hours field of
         * a <code>Calendar</code>, this would return
         * <code>Calendar.HOUR</code>. If there is no corresponding
         * <code>Calendar</code> constant, this will return -1.
         *
         * @return Calendar constant for this field
         * @see java.util.Calendar
         */
        public int getCalendarField() {
            return calendarField;
        }

        
Resolves instances being deserialized to the predefined constants.

Throws:
  • InvalidObjectException – if the constant could not be
        resolved.
Returns:resolved DateFormat.Field constant
/**
         * Resolves instances being deserialized to the predefined constants.
         *
         * @throws InvalidObjectException if the constant could not be
         *         resolved.
         * @return resolved DateFormat.Field constant
         */
        @Override
        protected Object readResolve() throws InvalidObjectException {
            if (this.getClass() != DateFormat.Field.class) {
                throw new InvalidObjectException("subclass didn't correctly implement readResolve");
            }

            Object instance = instanceMap.get(getName());
            if (instance != null) {
                return instance;
            } else {
                throw new InvalidObjectException("unknown attribute name");
            }
        }

        //
        // The constants
        //

        
Constant identifying the era field.

/**
         * Constant identifying the era field.
         */
        public static final Field ERA = new Field("era", Calendar.ERA);

        
Constant identifying the year field.

/**
         * Constant identifying the year field.
         */
        public static final Field YEAR = new Field("year", Calendar.YEAR);

        
Constant identifying the month field.

/**
         * Constant identifying the month field.
         */
        public static final Field MONTH = new Field("month", Calendar.MONTH);

        
Constant identifying the day of month field.

/**
         * Constant identifying the day of month field.
         */
        public static final Field DAY_OF_MONTH = new
                            Field("day of month", Calendar.DAY_OF_MONTH);

        
Constant identifying the hour of day field, where the legal values
are 1 to 24.

/**
         * Constant identifying the hour of day field, where the legal values
         * are 1 to 24.
         */
        public static final Field HOUR_OF_DAY1 = new Field("hour of day 1",-1);

        
Constant identifying the hour of day field, where the legal values
are 0 to 23.

/**
         * Constant identifying the hour of day field, where the legal values
         * are 0 to 23.
         */
        public static final Field HOUR_OF_DAY0 = new
               Field("hour of day", Calendar.HOUR_OF_DAY);

        
Constant identifying the minute field.

/**
         * Constant identifying the minute field.
         */
        public static final Field MINUTE =new Field("minute", Calendar.MINUTE);

        
Constant identifying the second field.

/**
         * Constant identifying the second field.
         */
        public static final Field SECOND =new Field("second", Calendar.SECOND);

        
Constant identifying the millisecond field.

/**
         * Constant identifying the millisecond field.
         */
        public static final Field MILLISECOND = new
                Field("millisecond", Calendar.MILLISECOND);

        
Constant identifying the day of week field.

/**
         * Constant identifying the day of week field.
         */
        public static final Field DAY_OF_WEEK = new
                Field("day of week", Calendar.DAY_OF_WEEK);

        
Constant identifying the day of year field.

/**
         * Constant identifying the day of year field.
         */
        public static final Field DAY_OF_YEAR = new
                Field("day of year", Calendar.DAY_OF_YEAR);

        
Constant identifying the day of week field.

/**
         * Constant identifying the day of week field.
         */
        public static final Field DAY_OF_WEEK_IN_MONTH =
                     new Field("day of week in month",
                                            Calendar.DAY_OF_WEEK_IN_MONTH);

        
Constant identifying the week of year field.

/**
         * Constant identifying the week of year field.
         */
        public static final Field WEEK_OF_YEAR = new
              Field("week of year", Calendar.WEEK_OF_YEAR);

        
Constant identifying the week of month field.

/**
         * Constant identifying the week of month field.
         */
        public static final Field WEEK_OF_MONTH = new
            Field("week of month", Calendar.WEEK_OF_MONTH);

        
Constant identifying the time of day indicator
(e.g. "a.m." or "p.m.") field.

/**
         * Constant identifying the time of day indicator
         * (e.g. "a.m." or "p.m.") field.
         */
        public static final Field AM_PM = new
                            Field("am pm", Calendar.AM_PM);

        
Constant identifying the hour field, where the legal values are
1 to 12.

/**
         * Constant identifying the hour field, where the legal values are
         * 1 to 12.
         */
        public static final Field HOUR1 = new Field("hour 1", -1);

        
Constant identifying the hour field, where the legal values are
0 to 11.

/**
         * Constant identifying the hour field, where the legal values are
         * 0 to 11.
         */
        public static final Field HOUR0 = new
                            Field("hour", Calendar.HOUR);

        
Constant identifying the time zone field.

/**
         * Constant identifying the time zone field.
         */
        public static final Field TIME_ZONE = new Field("time zone", -1);
    }
}