/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.lang3.time;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.io.Serializable;
  import java.text.DateFormatSymbols;
  import java.text.ParseException;
  import java.text.ParsePosition;
  import java.text.SimpleDateFormat;
  import java.util.ArrayList;
  import java.util.Calendar;
  import java.util.Comparator;
  import java.util.Date;
  import java.util.HashMap;
  import java.util.List;
  import java.util.ListIterator;
  import java.util.Locale;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  import java.util.TimeZone;
  import java.util.TreeSet;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import org.apache.commons.lang3.LocaleUtils;
  
  /**
   * FastDateParser is a fast and thread-safe version of {@link java.text.SimpleDateFormat}.
   *
   * <p>
   * To obtain a proxy to a FastDateParser, use {@link FastDateFormat#getInstance(String, TimeZone, Locale)} or another variation of the factory methods of
   * {@link FastDateFormat}.
   * </p>
   *
   * <p>
   * Since FastDateParser is thread safe, you can use a static member instance:
   * </p>
   * <code>
   *     private static final DateParser DATE_PARSER = FastDateFormat.getInstance("yyyy-MM-dd");
   * </code>
   *
   * <p>
   * This class can be used as a direct replacement for {@link SimpleDateFormat} in most parsing situations. This class is especially useful in multi-threaded
   * server environments. {@link SimpleDateFormat} is not thread-safe in any JDK version, nor will it be as Sun has closed the
   * <a href="https://bugs.openjdk.org/browse/JDK-4228335">bug</a>/RFE.
   * </p>
   *
   * <p>
   * Only parsing is supported by this class, but all patterns are compatible with SimpleDateFormat.
   * </p>
   *
   * <p>
   * The class operates in lenient mode, so for example a time of 90 minutes is treated as 1 hour 30 minutes.
   * </p>
   *
   * <p>
   * Timing tests indicate this class is as about as fast as SimpleDateFormat in single thread applications and about 25% faster in multi-thread applications.
   * </p>
   *
   * @since 3.2
   * @see FastDatePrinter
   */
  public class FastDateParser implements DateParser, Serializable {
  
      /**
       * A strategy that handles a text field in the parsing pattern
       */
      private static final class CaseInsensitiveTextStrategy extends PatternStrategy {
          private final int field;
          final Locale locale;
          private final Map<String, Integer> lKeyValues;
  
          /**
           * Constructs a Strategy that parses a Text field
           *
           * @param field            The Calendar field
           * @param definingCalendar The Calendar to use
           * @param locale           The Locale to use
           */
          CaseInsensitiveTextStrategy(final int field, final Calendar definingCalendar, final Locale locale) {
             this.field = field;
             this.locale = LocaleUtils.toLocale(locale);
 
             final StringBuilder regex = new StringBuilder();
             regex.append("((?iu)");
             lKeyValues = appendDisplayNames(definingCalendar, locale, field, regex);
             regex.setLength(regex.length() - 1);
             regex.append(")");
             createPattern(regex);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         void setCalendar(final FastDateParser parser, final Calendar calendar, final String value) {
             final String lowerCase = value.toLowerCase(locale);
             Integer iVal = lKeyValues.get(lowerCase);
             if (iVal == null) {
                 // match missing the optional trailing period
                 iVal = lKeyValues.get(lowerCase + '.');
             }
             // LANG-1669: Mimic fix done in OpenJDK 17 to resolve issue with parsing newly supported day periods added in OpenJDK 16
             if (Calendar.AM_PM != this.field || iVal <= 1) {
                 calendar.set(field, iVal.intValue());
             }
         }
 
         /**
          * Converts this instance to a handy debug string.
          *
          * @since 3.12.0
          */
         @Override
         public String toString() {
             return "CaseInsensitiveTextStrategy [field=" + field + ", locale=" + locale + ", lKeyValues=" + lKeyValues + ", pattern=" + pattern + "]";
         }
     }
 
     /**
      * A strategy that copies the static or quoted field in the parsing pattern
      */
     private static final class CopyQuotedStrategy extends Strategy {
 
         private final String formatField;
 
         /**
          * Constructs a Strategy that ensures the formatField has literal text
          *
          * @param formatField The literal text to match
          */
         CopyQuotedStrategy(final String formatField) {
             this.formatField = formatField;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         boolean isNumber() {
             return false;
         }
 
         @Override
         boolean parse(final FastDateParser parser, final Calendar calendar, final String source, final ParsePosition pos, final int maxWidth) {
             for (int idx = 0; idx < formatField.length(); ++idx) {
                 final int sIdx = idx + pos.getIndex();
                 if (sIdx == source.length()) {
                     pos.setErrorIndex(sIdx);
                     return false;
                 }
                 if (formatField.charAt(idx) != source.charAt(sIdx)) {
                     pos.setErrorIndex(sIdx);
                     return false;
                 }
             }
             pos.setIndex(formatField.length() + pos.getIndex());
             return true;
         }
 
         /**
          * Converts this instance to a handy debug string.
          *
          * @since 3.12.0
          */
         @Override
         public String toString() {
             return "CopyQuotedStrategy [formatField=" + formatField + "]";
         }
     }
 
     private static final class ISO8601TimeZoneStrategy extends PatternStrategy {
         // Z, +hh, -hh, +hhmm, -hhmm, +hh:mm or -hh:mm
 
         private static final Strategy ISO_8601_1_STRATEGY = new ISO8601TimeZoneStrategy("(Z|(?:[+-]\\d{2}))");
 
         private static final Strategy ISO_8601_2_STRATEGY = new ISO8601TimeZoneStrategy("(Z|(?:[+-]\\d{2}\\d{2}))");
 
         private static final Strategy ISO_8601_3_STRATEGY = new ISO8601TimeZoneStrategy("(Z|(?:[+-]\\d{2}(?::)\\d{2}))");
         /**
          * Factory method for ISO8601TimeZoneStrategies.
          *
          * @param tokenLen a token indicating the length of the TimeZone String to be formatted.
          * @return a ISO8601TimeZoneStrategy that can format TimeZone String of length {@code tokenLen}. If no such strategy exists, an IllegalArgumentException
          *         will be thrown.
          */
         static Strategy getStrategy(final int tokenLen) {
             switch (tokenLen) {
             case 1:
                 return ISO_8601_1_STRATEGY;
             case 2:
                 return ISO_8601_2_STRATEGY;
             case 3:
                 return ISO_8601_3_STRATEGY;
             default:
                 throw new IllegalArgumentException("invalid number of X");
             }
         }
         /**
          * Constructs a Strategy that parses a TimeZone
          *
          * @param pattern The Pattern
          */
         ISO8601TimeZoneStrategy(final String pattern) {
             createPattern(pattern);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         void setCalendar(final FastDateParser parser, final Calendar calendar, final String value) {
             calendar.setTimeZone(FastTimeZone.getGmtTimeZone(value));
         }
     }
 
     /**
      * A strategy that handles a number field in the parsing pattern
      */
     private static class NumberStrategy extends Strategy {
 
         private final int field;
 
         /**
          * Constructs a Strategy that parses a Number field
          *
          * @param field The Calendar field
          */
         NumberStrategy(final int field) {
             this.field = field;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         boolean isNumber() {
             return true;
         }
 
         /**
          * Make any modifications to parsed integer
          *
          * @param parser The parser
          * @param iValue The parsed integer
          * @return The modified value
          */
         int modify(final FastDateParser parser, final int iValue) {
             return iValue;
         }
 
         @Override
         boolean parse(final FastDateParser parser, final Calendar calendar, final String source, final ParsePosition pos, final int maxWidth) {
             int idx = pos.getIndex();
             int last = source.length();
 
             if (maxWidth == 0) {
                 // if no maxWidth, strip leading white space
                 for (; idx < last; ++idx) {
                     final char c = source.charAt(idx);
                     if (!Character.isWhitespace(c)) {
                         break;
                     }
                 }
                 pos.setIndex(idx);
             } else {
                 final int end = idx + maxWidth;
                 if (last > end) {
                     last = end;
                 }
             }
 
             for (; idx < last; ++idx) {
                 final char c = source.charAt(idx);
                 if (!Character.isDigit(c)) {
                     break;
                 }
             }
 
             if (pos.getIndex() == idx) {
                 pos.setErrorIndex(idx);
                 return false;
             }
 
             final int value = Integer.parseInt(source.substring(pos.getIndex(), idx));
             pos.setIndex(idx);
 
             calendar.set(field, modify(parser, value));
             return true;
         }
 
         /**
          * Converts this instance to a handy debug string.
          *
          * @since 3.12.0
          */
         @Override
         public String toString() {
             return "NumberStrategy [field=" + field + "]";
         }
     }
 
     /**
      * A strategy to parse a single field from the parsing pattern
      */
     private abstract static class PatternStrategy extends Strategy {
 
         Pattern pattern;
 
         void createPattern(final String regex) {
             this.pattern = Pattern.compile(regex);
         }
 
         void createPattern(final StringBuilder regex) {
             createPattern(regex.toString());
         }
 
         /**
          * Is this field a number? The default implementation returns false.
          *
          * @return true, if field is a number
          */
         @Override
         boolean isNumber() {
             return false;
         }
 
         @Override
         boolean parse(final FastDateParser parser, final Calendar calendar, final String source, final ParsePosition pos, final int maxWidth) {
             final Matcher matcher = pattern.matcher(source.substring(pos.getIndex()));
             if (!matcher.lookingAt()) {
                 pos.setErrorIndex(pos.getIndex());
                 return false;
             }
             pos.setIndex(pos.getIndex() + matcher.end(1));
             setCalendar(parser, calendar, matcher.group(1));
             return true;
         }
 
         abstract void setCalendar(FastDateParser parser, Calendar calendar, String value);
 
         /**
          * Converts this instance to a handy debug string.
          *
          * @since 3.12.0
          */
         @Override
         public String toString() {
             return getClass().getSimpleName() + " [pattern=" + pattern + "]";
         }
 
     }
 
     /**
      * A strategy to parse a single field from the parsing pattern
      */
     private abstract static class Strategy {
 
         /**
          * Is this field a number? The default implementation returns false.
          *
          * @return true, if field is a number
          */
         boolean isNumber() {
             return false;
         }
 
         abstract boolean parse(FastDateParser parser, Calendar calendar, String source, ParsePosition pos, int maxWidth);
     }
 
     /**
      * Holds strategy and field width
      */
     private static final class StrategyAndWidth {
 
         final Strategy strategy;
         final int width;
 
         StrategyAndWidth(final Strategy strategy, final int width) {
             this.strategy = Objects.requireNonNull(strategy, "strategy");
             this.width = width;
         }
 
         int getMaxWidth(final ListIterator<StrategyAndWidth> lt) {
             if (!strategy.isNumber() || !lt.hasNext()) {
                 return 0;
             }
             final Strategy nextStrategy = lt.next().strategy;
             lt.previous();
             return nextStrategy.isNumber() ? width : 0;
         }
 
         @Override
         public String toString() {
             return "StrategyAndWidth [strategy=" + strategy + ", width=" + width + "]";
         }
     }
 
     /**
      * Parse format into Strategies
      */
     private final class StrategyParser {
         private final Calendar definingCalendar;
         private int currentIdx;
 
         StrategyParser(final Calendar definingCalendar) {
             this.definingCalendar = Objects.requireNonNull(definingCalendar, "definingCalendar");
         }
 
         StrategyAndWidth getNextStrategy() {
             if (currentIdx >= pattern.length()) {
                 return null;
             }
 
             final char c = pattern.charAt(currentIdx);
             if (isFormatLetter(c)) {
                 return letterPattern(c);
             }
             return literal();
         }
 
         private StrategyAndWidth letterPattern(final char c) {
             final int begin = currentIdx;
             while (++currentIdx < pattern.length()) {
                 if (pattern.charAt(currentIdx) != c) {
                     break;
                 }
             }
 
             final int width = currentIdx - begin;
             return new StrategyAndWidth(getStrategy(c, width, definingCalendar), width);
         }
 
         private StrategyAndWidth literal() {
             boolean activeQuote = false;
 
             final StringBuilder sb = new StringBuilder();
             while (currentIdx < pattern.length()) {
                 final char c = pattern.charAt(currentIdx);
                 if (!activeQuote && isFormatLetter(c)) {
                     break;
                 }
                 if (c == '\'' && (++currentIdx == pattern.length() || pattern.charAt(currentIdx) != '\'')) {
                     activeQuote = !activeQuote;
                     continue;
                 }
                 ++currentIdx;
                 sb.append(c);
             }
 
             if (activeQuote) {
                 throw new IllegalArgumentException("Unterminated quote");
             }
 
             final String formatField = sb.toString();
             return new StrategyAndWidth(new CopyQuotedStrategy(formatField), formatField.length());
         }
     }
 
     /**
      * A strategy that handles a time zone field in the parsing pattern
      */
     static class TimeZoneStrategy extends PatternStrategy {
         private static final class TzInfo {
             final TimeZone zone;
             final int dstOffset;
 
             TzInfo(final TimeZone tz, final boolean useDst) {
                 zone = tz;
                 dstOffset = useDst ? tz.getDSTSavings() : 0;
             }
 
             @Override
             public String toString() {
                 return "TzInfo [zone=" + zone + ", dstOffset=" + dstOffset + "]";
             }
         }
         private static final String RFC_822_TIME_ZONE = "[+-]\\d{4}";
 
         private static final String GMT_OPTION = TimeZones.GMT_ID + "[+-]\\d{1,2}:\\d{2}";
         /**
          * Index of zone id
          */
         private static final int ID = 0;
 
         private final Locale locale;
 
         private final Map<String, TzInfo> tzNames = new HashMap<>();
 
         /**
          * Constructs a Strategy that parses a TimeZone
          *
          * @param locale The Locale
          */
         TimeZoneStrategy(final Locale locale) {
             this.locale = LocaleUtils.toLocale(locale);
 
             final StringBuilder sb = new StringBuilder();
             sb.append("((?iu)" + RFC_822_TIME_ZONE + "|" + GMT_OPTION);
 
             final Set<String> sorted = new TreeSet<>(LONGER_FIRST_LOWERCASE);
 
             // Order is undefined.
             // TODO Use of getZoneStrings() is discouraged per its Javadoc.
             final String[][] zones = DateFormatSymbols.getInstance(locale).getZoneStrings();
             for (final String[] zoneNames : zones) {
                 // offset 0 is the time zone ID and is not localized
                 final String tzId = zoneNames[ID];
                 if (tzId.equalsIgnoreCase(TimeZones.GMT_ID)) {
                     continue;
                 }
                 final TimeZone tz = TimeZone.getTimeZone(tzId);
                 // offset 1 is long standard name
                 // offset 2 is short standard name
                 final TzInfo standard = new TzInfo(tz, false);
                 TzInfo tzInfo = standard;
                 for (int i = 1; i < zoneNames.length; ++i) {
                     switch (i) {
                     case 3: // offset 3 is long daylight savings (or summertime) name
                             // offset 4 is the short summertime name
                         tzInfo = new TzInfo(tz, true);
                         break;
                     case 5: // offset 5 starts additional names, probably standard time
                         tzInfo = standard;
                         break;
                     default:
                         break;
                     }
                     final String zoneName = zoneNames[i];
                     if (zoneName != null) {
                         final String key = zoneName.toLowerCase(locale);
                         // ignore the data associated with duplicates supplied in
                         // the additional names
                         if (sorted.add(key)) {
                             tzNames.put(key, tzInfo);
                         }
                     }
                 }
             }
 
             // Order is undefined.
             for (final String tzId : TimeZone.getAvailableIDs()) {
                 if (tzId.equalsIgnoreCase(TimeZones.GMT_ID)) {
                     continue;
                 }
                 final TimeZone tz = TimeZone.getTimeZone(tzId);
                 final String zoneName = tz.getDisplayName(locale);
                 final String key = zoneName.toLowerCase(locale);
                 if (sorted.add(key)) {
                     tzNames.put(key, new TzInfo(tz, tz.observesDaylightTime()));
                 }
             }
 
             // order the regex alternatives with longer strings first, greedy
             // match will ensure the longest string will be consumed
             sorted.forEach(zoneName -> simpleQuote(sb.append('|'), zoneName));
             sb.append(")");
             createPattern(sb);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         void setCalendar(final FastDateParser parser, final Calendar calendar, final String timeZone) {
             final TimeZone tz = FastTimeZone.getGmtTimeZone(timeZone);
             if (tz != null) {
                 calendar.setTimeZone(tz);
             } else {
                 final String lowerCase = timeZone.toLowerCase(locale);
                 TzInfo tzInfo = tzNames.get(lowerCase);
                 if (tzInfo == null) {
                     // match missing the optional trailing period
                     tzInfo = tzNames.get(lowerCase + '.');
                 }
                 calendar.set(Calendar.DST_OFFSET, tzInfo.dstOffset);
                 calendar.set(Calendar.ZONE_OFFSET, tzInfo.zone.getRawOffset());
             }
         }
 
         /**
          * Converts this instance to a handy debug string.
          *
          * @since 3.12.0
          */
         @Override
         public String toString() {
             return "TimeZoneStrategy [locale=" + locale + ", tzNames=" + tzNames + ", pattern=" + pattern + "]";
         }
 
     }
 
     /**
      * Required for serialization support.
      *
      * @see java.io.Serializable
      */
     private static final long serialVersionUID = 3L;
 
     static final Locale JAPANESE_IMPERIAL = new Locale("ja", "JP", "JP");
 
     /**
      * comparator used to sort regex alternatives. Alternatives should be ordered longer first, and shorter last. ('february' before 'feb'). All entries must be
      * lower-case by locale.
      */
     private static final Comparator<String> LONGER_FIRST_LOWERCASE = Comparator.reverseOrder();
 
     // helper classes to parse the format string
 
     @SuppressWarnings("unchecked") // OK because we are creating an array with no entries
     private static final ConcurrentMap<Locale, Strategy>[] caches = new ConcurrentMap[Calendar.FIELD_COUNT];
 
     private static final Strategy ABBREVIATED_YEAR_STRATEGY = new NumberStrategy(Calendar.YEAR) {
         /**
          * {@inheritDoc}
          */
         @Override
         int modify(final FastDateParser parser, final int iValue) {
             return iValue < 100 ? parser.adjustYear(iValue) : iValue;
         }
     };
 
     private static final Strategy NUMBER_MONTH_STRATEGY = new NumberStrategy(Calendar.MONTH) {
         @Override
         int modify(final FastDateParser parser, final int iValue) {
             return iValue - 1;
         }
     };
 
     private static final Strategy LITERAL_YEAR_STRATEGY = new NumberStrategy(Calendar.YEAR);
 
     private static final Strategy WEEK_OF_YEAR_STRATEGY = new NumberStrategy(Calendar.WEEK_OF_YEAR);
 
     private static final Strategy WEEK_OF_MONTH_STRATEGY = new NumberStrategy(Calendar.WEEK_OF_MONTH);
 
     private static final Strategy DAY_OF_YEAR_STRATEGY = new NumberStrategy(Calendar.DAY_OF_YEAR);
 
     private static final Strategy DAY_OF_MONTH_STRATEGY = new NumberStrategy(Calendar.DAY_OF_MONTH);
 
     private static final Strategy DAY_OF_WEEK_STRATEGY = new NumberStrategy(Calendar.DAY_OF_WEEK) {
         @Override
         int modify(final FastDateParser parser, final int iValue) {
             return iValue == 7 ? Calendar.SUNDAY : iValue + 1;
         }
     };
 
     private static final Strategy DAY_OF_WEEK_IN_MONTH_STRATEGY = new NumberStrategy(Calendar.DAY_OF_WEEK_IN_MONTH);
 
     private static final Strategy HOUR_OF_DAY_STRATEGY = new NumberStrategy(Calendar.HOUR_OF_DAY);
 
     private static final Strategy HOUR24_OF_DAY_STRATEGY = new NumberStrategy(Calendar.HOUR_OF_DAY) {
         @Override
         int modify(final FastDateParser parser, final int iValue) {
             return iValue == 24 ? 0 : iValue;
         }
     };
 
     private static final Strategy HOUR12_STRATEGY = new NumberStrategy(Calendar.HOUR) {
         @Override
         int modify(final FastDateParser parser, final int iValue) {
             return iValue == 12 ? 0 : iValue;
         }
     };
 
     private static final Strategy HOUR_STRATEGY = new NumberStrategy(Calendar.HOUR);
 
     private static final Strategy MINUTE_STRATEGY = new NumberStrategy(Calendar.MINUTE);
 
     private static final Strategy SECOND_STRATEGY = new NumberStrategy(Calendar.SECOND);
 
     // Support for strategies
 
     private static final Strategy MILLISECOND_STRATEGY = new NumberStrategy(Calendar.MILLISECOND);
 
     /**
      * Gets the short and long values displayed for a field
      *
      * @param calendar The calendar to obtain the short and long values
      * @param locale   The locale of display names
      * @param field    The field of interest
      * @param regex    The regular expression to build
      * @return The map of string display names to field values
      */
     private static Map<String, Integer> appendDisplayNames(final Calendar calendar, final Locale locale, final int field, final StringBuilder regex) {
         Objects.requireNonNull(calendar, "calendar");
         final Map<String, Integer> values = new HashMap<>();
         final Locale actualLocale = LocaleUtils.toLocale(locale);
         final Map<String, Integer> displayNames = calendar.getDisplayNames(field, Calendar.ALL_STYLES, actualLocale);
         final TreeSet<String> sorted = new TreeSet<>(LONGER_FIRST_LOWERCASE);
         displayNames.forEach((k, v) -> {
             final String keyLc = k.toLowerCase(actualLocale);
             if (sorted.add(keyLc)) {
                 values.put(keyLc, v);
             }
         });
         sorted.forEach(symbol -> simpleQuote(regex, symbol).append('|'));
         return values;
     }
 
     /**
      * Gets a cache of Strategies for a particular field
      *
      * @param field The Calendar field
      * @return a cache of Locale to Strategy
      */
     private static ConcurrentMap<Locale, Strategy> getCache(final int field) {
         synchronized (caches) {
             if (caches[field] == null) {
                 caches[field] = new ConcurrentHashMap<>(3);
             }
             return caches[field];
         }
     }
 
     private static boolean isFormatLetter(final char c) {
         return c >= 'A' && c <= 'Z' || c >= 'a' && c <= 'z';
     }
 
     private static StringBuilder simpleQuote(final StringBuilder sb, final String value) {
         for (int i = 0; i < value.length(); ++i) {
             final char c = value.charAt(i);
             switch (c) {
             case '\\':
             case '^':
             case '$':
             case '.':
             case '|':
             case '?':
             case '*':
             case '+':
             case '(':
             case ')':
             case '[':
             case '{':
                 sb.append('\\');
             default:
                 sb.append(c);
             }
         }
         if (sb.charAt(sb.length() - 1) == '.') {
             // trailing '.' is optional
             sb.append('?');
         }
         return sb;
     }
 
     /** Input pattern. */
     private final String pattern;
 
     /** Input TimeZone. */
     private final TimeZone timeZone;
 
     /** Input Locale. */
     private final Locale locale;
 
     /**
      * Century from Date.
      */
     private final int century;
 
     /**
      * Start year from Date.
      */
     private final int startYear;
 
     /** Initialized from Calendar. */
     private transient List<StrategyAndWidth> patterns;
 
     /**
      * Constructs a new FastDateParser.
      *
      * Use {@link FastDateFormat#getInstance(String, TimeZone, Locale)} or another variation of the factory methods of {@link FastDateFormat} to get a cached
      * FastDateParser instance.
      *
      * @param pattern  non-null {@link java.text.SimpleDateFormat} compatible pattern
      * @param timeZone non-null time zone to use
      * @param locale   non-null locale
      */
     protected FastDateParser(final String pattern, final TimeZone timeZone, final Locale locale) {
         this(pattern, timeZone, locale, null);
     }
 
     /**
      * Constructs a new FastDateParser.
      *
      * @param pattern      non-null {@link java.text.SimpleDateFormat} compatible pattern
      * @param timeZone     non-null time zone to use
      * @param locale       locale, null maps to the default Locale.
      * @param centuryStart The start of the century for 2 digit year parsing
      *
      * @since 3.5
      */
     protected FastDateParser(final String pattern, final TimeZone timeZone, final Locale locale, final Date centuryStart) {
         this.pattern = Objects.requireNonNull(pattern, "pattern");
         this.timeZone = Objects.requireNonNull(timeZone, "timeZone");
         this.locale = LocaleUtils.toLocale(locale);
 
         final Calendar definingCalendar = Calendar.getInstance(timeZone, this.locale);
 
         final int centuryStartYear;
         if (centuryStart != null) {
             definingCalendar.setTime(centuryStart);
             centuryStartYear = definingCalendar.get(Calendar.YEAR);
         } else if (this.locale.equals(JAPANESE_IMPERIAL)) {
             centuryStartYear = 0;
         } else {
             // from 80 years ago to 20 years from now
             definingCalendar.setTime(new Date());
             centuryStartYear = definingCalendar.get(Calendar.YEAR) - 80;
         }
         century = centuryStartYear / 100 * 100;
         startYear = centuryStartYear - century;
 
         init(definingCalendar);
     }
 
     /**
      * Adjusts dates to be within appropriate century
      *
      * @param twoDigitYear The year to adjust
      * @return A value between centuryStart(inclusive) to centuryStart+100(exclusive)
      */
     private int adjustYear(final int twoDigitYear) {
         final int trial = century + twoDigitYear;
         return twoDigitYear >= startYear ? trial : trial + 100;
     }
 
     // Basics
     /**
      * Compares another object for equality with this object.
      *
      * @param obj the object to compare to
      * @return {@code true}if equal to this instance
      */
     @Override
     public boolean equals(final Object obj) {
         if (!(obj instanceof FastDateParser)) {
             return false;
         }
         final FastDateParser other = (FastDateParser) obj;
         return pattern.equals(other.pattern) && timeZone.equals(other.timeZone) && locale.equals(other.locale);
     }
 
     /*
      * (non-Javadoc)
      *
      * @see org.apache.commons.lang3.time.DateParser#getLocale()
      */
     @Override
     public Locale getLocale() {
         return locale;
     }
 
     /**
      * Constructs a Strategy that parses a Text field
      *
      * @param field            The Calendar field
      * @param definingCalendar The calendar to obtain the short and long values
      * @return a TextStrategy for the field and Locale
      */
     private Strategy getLocaleSpecificStrategy(final int field, final Calendar definingCalendar) {
         final ConcurrentMap<Locale, Strategy> cache = getCache(field);
         return cache.computeIfAbsent(locale,
                 k -> field == Calendar.ZONE_OFFSET ? new TimeZoneStrategy(locale) : new CaseInsensitiveTextStrategy(field, definingCalendar, locale));
     }
     // Accessors
     /*
      * (non-Javadoc)
      *
      * @see org.apache.commons.lang3.time.DateParser#getPattern()
      */
     @Override
     public String getPattern() {
         return pattern;
     }
     /**
      * Gets a Strategy given a field from a SimpleDateFormat pattern
      *
      * @param f                A sub-sequence of the SimpleDateFormat pattern
      * @param width            formatting width
      * @param definingCalendar The calendar to obtain the short and long values
      * @return The Strategy that will handle parsing for the field
      */
     private Strategy getStrategy(final char f, final int width, final Calendar definingCalendar) {
         switch (f) {
         default:
             throw new IllegalArgumentException("Format '" + f + "' not supported");
         case 'D':
             return DAY_OF_YEAR_STRATEGY;
         case 'E':
             return getLocaleSpecificStrategy(Calendar.DAY_OF_WEEK, definingCalendar);
         case 'F':
             return DAY_OF_WEEK_IN_MONTH_STRATEGY;
         case 'G':
             return getLocaleSpecificStrategy(Calendar.ERA, definingCalendar);
         case 'H': // Hour in day (0-23)
             return HOUR_OF_DAY_STRATEGY;
         case 'K': // Hour in am/pm (0-11)
             return HOUR_STRATEGY;
         case 'M':
         case 'L':
             return width >= 3 ? getLocaleSpecificStrategy(Calendar.MONTH, definingCalendar) : NUMBER_MONTH_STRATEGY;
         case 'S':
             return MILLISECOND_STRATEGY;
         case 'W':
             return WEEK_OF_MONTH_STRATEGY;
         case 'a':
             return getLocaleSpecificStrategy(Calendar.AM_PM, definingCalendar);
         case 'd':
             return DAY_OF_MONTH_STRATEGY;
         case 'h': // Hour in am/pm (1-12), i.e. midday/midnight is 12, not 0
             return HOUR12_STRATEGY;
         case 'k': // Hour in day (1-24), i.e. midnight is 24, not 0
             return HOUR24_OF_DAY_STRATEGY;
         case 'm':
             return MINUTE_STRATEGY;
         case 's':
             return SECOND_STRATEGY;
         case 'u':
             return DAY_OF_WEEK_STRATEGY;
         case 'w':
             return WEEK_OF_YEAR_STRATEGY;
         case 'y':
         case 'Y':
             return width > 2 ? LITERAL_YEAR_STRATEGY : ABBREVIATED_YEAR_STRATEGY;
         case 'X':
             return ISO8601TimeZoneStrategy.getStrategy(width);
         case 'Z':
             if (width == 2) {
                 return ISO8601TimeZoneStrategy.ISO_8601_3_STRATEGY;
             }
             //$FALL-THROUGH$
         case 'z':
             return getLocaleSpecificStrategy(Calendar.ZONE_OFFSET, definingCalendar);
         }
     }
     /*
      * (non-Javadoc)
      *
      * @see org.apache.commons.lang3.time.DateParser#getTimeZone()
      */
     @Override
     public TimeZone getTimeZone() {
         return timeZone;
     }
     /**
      * Returns a hash code compatible with equals.
      *
      * @return a hash code compatible with equals
      */
     @Override
     public int hashCode() {
         return pattern.hashCode() + 13 * (timeZone.hashCode() + 13 * locale.hashCode());
     }
     /**
      * Initializes derived fields from defining fields. This is called from constructor and from readObject (de-serialization)
      *
      * @param definingCalendar the {@link java.util.Calendar} instance used to initialize this FastDateParser
      */
     private void init(final Calendar definingCalendar) {
         patterns = new ArrayList<>();
 
         final StrategyParser strategyParser = new StrategyParser(definingCalendar);
         for (;;) {
             final StrategyAndWidth field = strategyParser.getNextStrategy();
             if (field == null) {
                 break;
             }
             patterns.add(field);
         }
     }
 
     /*
      * (non-Javadoc)
      *
      * @see org.apache.commons.lang3.time.DateParser#parse(String)
      */
     @Override
     public Date parse(final String source) throws ParseException {
         final ParsePosition pp = new ParsePosition(0);
         final Date date = parse(source, pp);
         if (date == null) {
             // Add a note regarding supported date range
             if (locale.equals(JAPANESE_IMPERIAL)) {
                 throw new ParseException("(The " + locale + " locale does not support dates before 1868 AD)\nUnparseable date: \"" + source,
                         pp.getErrorIndex());
             }
             throw new ParseException("Unparseable date: " + source, pp.getErrorIndex());
         }
         return date;
     }
     /**
      * This implementation updates the ParsePosition if the parse succeeds. However, it sets the error index to the position before the failed field unlike the
      * method {@link java.text.SimpleDateFormat#parse(String, ParsePosition)} which sets the error index to after the failed field.
      * <p>
      * To determine if the parse has succeeded, the caller must check if the current parse position given by {@link ParsePosition#getIndex()} has been updated.
      * If the input buffer has been fully parsed, then the index will point to just after the end of the input buffer.
      *
      * @see org.apache.commons.lang3.time.DateParser#parse(String, java.text.ParsePosition)
      */
     @Override
     public Date parse(final String source, final ParsePosition pos) {
         // timing tests indicate getting new instance is 19% faster than cloning
         final Calendar cal = Calendar.getInstance(timeZone, locale);
         cal.clear();
 
         return parse(source, pos, cal) ? cal.getTime() : null;
     }
     /**
      * Parses a formatted date string according to the format. Updates the Calendar with parsed fields. Upon success, the ParsePosition index is updated to
      * indicate how much of the source text was consumed. Not all source text needs to be consumed. Upon parse failure, ParsePosition error index is updated to
      * the offset of the source text which does not match the supplied format.
      *
      * @param source   The text to parse.
      * @param pos      On input, the position in the source to start parsing, on output, updated position.
      * @param calendar The calendar into which to set parsed fields.
      * @return true, if source has been parsed (pos parsePosition is updated); otherwise false (and pos errorIndex is updated)
      * @throws IllegalArgumentException when Calendar has been set to be not lenient, and a parsed field is out of range.
      */
     @Override
     public boolean parse(final String source, final ParsePosition pos, final Calendar calendar) {
         final ListIterator<StrategyAndWidth> lt = patterns.listIterator();
         while (lt.hasNext()) {
             final StrategyAndWidth strategyAndWidth = lt.next();
             final int maxWidth = strategyAndWidth.getMaxWidth(lt);
             if (!strategyAndWidth.strategy.parse(this, calendar, source, pos, maxWidth)) {
                 return false;
             }
         }
         return true;
     }
 
     /*
      * (non-Javadoc)
      *
      * @see org.apache.commons.lang3.time.DateParser#parseObject(String)
      */
     @Override
     public Object parseObject(final String source) throws ParseException {
         return parse(source);
     }
 
     /*
      * (non-Javadoc)
      *
      * @see org.apache.commons.lang3.time.DateParser#parseObject(String, java.text.ParsePosition)
      */
     @Override
     public Object parseObject(final String source, final ParsePosition pos) {
         return parse(source, pos);
     }
     // Serializing
     /**
      * Creates the object after serialization. This implementation reinitializes the transient properties.
      *
      * @param in ObjectInputStream from which the object is being deserialized.
      * @throws IOException            if there is an IO issue.
      * @throws ClassNotFoundException if a class cannot be found.
      */
     private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
         in.defaultReadObject();
 
         final Calendar definingCalendar = Calendar.getInstance(timeZone, locale);
         init(definingCalendar);
     }
     /**
      * Gets a string version of this formatter.
      *
      * @return a debugging string
      */
     @Override
     public String toString() {
         return "FastDateParser[" + pattern + ", " + locale + ", " + timeZone.getID() + "]";
     }
     /**
      * Converts all state of this instance to a String handy for debugging.
      *
      * @return a string.
      * @since 3.12.0
      */
     public String toStringAll() {
         return "FastDateParser [pattern=" + pattern + ", timeZone=" + timeZone + ", locale=" + locale + ", century=" + century + ", startYear=" + startYear
                 + ", patterns=" + patterns + "]";
     }
 }