/*
 * Copyright (c) 1996, 2017, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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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;

/**
 * {@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 → text), parsing (text → 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 {@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 <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.
 */
 public static final int ERA_FIELD = 0;
 /**
 * 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.
 */
 public static final int MONTH_FIELD = 2;
 /**
 * 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.
 */
 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.
 */
 public static final int HOUR_OF_DAY0_FIELD = 5;
 /**
 * 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.
 */
 public static final int SECOND_FIELD = 7;
 /**
 * 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.
 */
 public static final int DAY_OF_WEEK_FIELD = 9;
 /**
 * 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.
 */
 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.
 */
 public static final int WEEK_OF_YEAR_FIELD = 12;
 /**
 * 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.
 */
 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.
 */
 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.
 */
 public static final int HOUR0_FIELD = 16;
 /**
 * 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 {@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 {@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 {@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.
 * <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 {@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 <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.
 */
 public static final int FULL = 0;
 /**
 * Constant for long style pattern.
 */
 public static final int LONG = 1;
 /**
 * Constant for medium style pattern.
 */
 public static final int MEDIUM = 2;
 /**
 * Constant for short style pattern.
 */
 public static final int SHORT = 3;
 /**
 * 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 {@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 {@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.
 * @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 {@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 {@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.
 * @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 {@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 {@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.
 * @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.
 *
 * @return a date/time formatter
 */
 public static final DateFormat getInstance() {
 return getDateTimeInstance(SHORT, SHORT);
 }

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

 /**
 * 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.
 * @return the number formatter which this date/time formatter uses.
 */
 public NumberFormat getNumberFormat()
 {
 return numberFormat;
 }

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

 /**
 * 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
 */
 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.
 * @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.
 */
 protected DateFormat() {}

 /**
 * 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. */
 private int 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 <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 <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.
 * @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.
 */
 public static final Field ERA = new Field("era", Calendar.ERA);

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

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

 /**
 * 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.
 */
 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.
 */
 public static final Field HOUR_OF_DAY0 = new
 Field("hour of day", Calendar.HOUR_OF_DAY);

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

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

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

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

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

 /**
 * 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.
 */
 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.
 */
 public static final Field HOUR1 = new Field("hour 1", -1);

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