/*

 * Copyright (c) 1996, 2010, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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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.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:

 * <pre>

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

 * </pre>

 * <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.

 * <pre>

 *  DateFormat df = DateFormat.getDateInstance();

 *  for (int i = 0; i < myDate.length; ++i) {

 *    output.println(df.format(myDate[i]) + "; ");

 *  }

 * </pre>

 * <p>To format a date for a different Locale, specify it in the

 * call to {@link #getDateInstance(int, Locale) getDateInstance()}.

 * <pre>

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

 * </pre>

 * <p>You can use a DateFormat to parse also.

 * <pre>

 *  myDate = df.parse(myString);

 * </pre>

 * <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>

 *

 * <h4><a name="synchronization">Synchronization</a></h4>

 *

 * <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.

 *

 * @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

 */

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 final static int ERA_FIELD = 0;

    /**

     * Useful constant for YEAR field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int YEAR_FIELD = 1;

    /**

     * Useful constant for MONTH field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int MONTH_FIELD = 2;

    /**

     * Useful constant for DATE field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static 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 final static 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 final static int HOUR_OF_DAY0_FIELD = 5;

    /**

     * Useful constant for MINUTE field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int MINUTE_FIELD = 6;

    /**

     * Useful constant for SECOND field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int SECOND_FIELD = 7;

    /**

     * Useful constant for MILLISECOND field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int MILLISECOND_FIELD = 8;

    /**

     * Useful constant for DAY_OF_WEEK field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int DAY_OF_WEEK_FIELD = 9;

    /**

     * Useful constant for DAY_OF_YEAR field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int DAY_OF_YEAR_FIELD = 10;

    /**

     * Useful constant for DAY_OF_WEEK_IN_MONTH field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int DAY_OF_WEEK_IN_MONTH_FIELD = 11;

    /**

     * Useful constant for WEEK_OF_YEAR field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int WEEK_OF_YEAR_FIELD = 12;

    /**

     * Useful constant for WEEK_OF_MONTH field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int WEEK_OF_MONTH_FIELD = 13;

    /**

     * Useful constant for AM_PM field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static 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 final static 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 final static int HOUR0_FIELD = 16;

    /**

     * Useful constant for TIMEZONE field alignment.

     * Used in FieldPosition of date/time formatting.

     */

    public final static int TIMEZONE_FIELD = 17;

    // Proclaim serial compatibility with 1.1 FCS

    private static final long serialVersionUID = 7218322306649953788L;

    /**

     * Overrides Format.

     * Formats a time object into a time string. Examples of time objects

     * are a time value expressed in milliseconds and a Date object.

     * @param obj must be a Number or a Date.

     * @param toAppendTo the string buffer for the returning time string.

     * @return the string buffer passed in as toAppendTo, with formatted text appended.

     * @param fieldPosition keeps track of the position of the field

     * within the returned string.

     * On input: an alignment field,

     * if desired. On output: the offsets of the alignment field. For

     * example, given a time text "1996.07.10 AD at 15:08:56 PDT",

     * if the given fieldPosition is DateFormat.YEAR_FIELD, the

     * begin index and end index of fieldPosition will be set to

     * 0 and 4, respectively.

     * Notice that if the same time field appears

     * more than once in a pattern, the fieldPosition will be set for the first

     * occurrence of that time field. For instance, formatting a Date to

     * the time string "1 PM PDT (Pacific Daylight Time)" using the pattern

     * "h a z (zzzz)" and the alignment field DateFormat.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'.

     * @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.

     * @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 of the position of the field

     * within the returned string.

     * On input: an alignment field,

     * if desired. On output: the offsets of the alignment field. For

     * example, given a time text "1996.07.10 AD at 15:08:56 PDT",

     * if the given fieldPosition is DateFormat.YEAR_FIELD, the

     * begin index and end index of fieldPosition will be set to

     * 0 and 4, respectively.

     * Notice that if the same time field appears

     * more than once in a pattern, the fieldPosition will be set for the first

     * occurrence of that time field. For instance, formatting a Date to

     * the time string "1 PM PDT (Pacific Daylight Time)" using the pattern

     * "h a z (zzzz)" and the alignment field DateFormat.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'.

     * @return the string buffer passed in as toAppendTo, with formatted text appended.

     */

    public abstract StringBuffer format(Date date, StringBuffer toAppendTo,

                                        FieldPosition fieldPosition);

    /**

     * Formats a Date into a date/time string.

     * @param date the time value to be formatted into a time string.

     * @return the formatted 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.

     * @exception NullPointerException if <code>pos</code> 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 locale.

     * @return a time formatter.

     */

    public final static DateFormat getTimeInstance()

    {

        return get(DEFAULT, 0, 1, Locale.getDefault(Locale.Category.FORMAT));

    }

    /**

     * Gets the time formatter with the given formatting style

     * for the default locale.

     * @param style the given formatting style. For example,

     * SHORT for "h:mm a" in the US locale.

     * @return a time formatter.

     */

    public final static 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 final static DateFormat getTimeInstance(int style,

                                                 Locale aLocale)

    {

        return get(style, 0, 1, aLocale);

    }

    /**

     * Gets the date formatter with the default formatting style

     * for the default locale.

     * @return a date formatter.

     */

    public final static DateFormat getDateInstance()

    {

        return get(0, DEFAULT, 2, Locale.getDefault(Locale.Category.FORMAT));

    }

    /**

     * Gets the date formatter with the given formatting style

     * for the default locale.

     * @param style the given formatting style. For example,

     * SHORT for "M/d/yy" in the US locale.

     * @return a date formatter.

     */

    public final static 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 final static 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 locale.

     * @return a date/time formatter.

     */

    public final static DateFormat getDateTimeInstance()

    {

        return get(DEFAULT, DEFAULT, 3, Locale.getDefault(Locale.Category.FORMAT));

    }

    /**

     * Gets the date/time formatter with the given date and time