/*
    * 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.logging.log4j.core.util.datetime;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.io.Serializable;
  import java.text.DateFormat;
  import java.text.DateFormatSymbols;
  import java.text.FieldPosition;
  import java.util.ArrayList;
  import java.util.Calendar;
  import java.util.Date;
  import java.util.GregorianCalendar;
  import java.util.List;
  import java.util.Locale;
  import java.util.TimeZone;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  /**
   * Copied from Commons Lang 3
   *
   */
  public class FastDatePrinter implements DatePrinter, Serializable {
      // A lot of the speed in this class comes from caching, but some comes
      // from the special int to StringBuilder conversion.
      //
      // The following produces a padded 2 digit number:
      //   buffer.append((char)(value / 10 + '0'));
      //   buffer.append((char)(value % 10 + '0'));
      //
      // Note that the fastest append to StringBuilder is a single char (used here).
      // Note that Integer.toString() is not called, the conversion is simply
      // taking the value and adding (mathematically) the ASCII value for '0'.
      // So, don't change this code! It works and is very fast.
  
      /**
       * Required for serialization support.
       *
       * @see java.io.Serializable
       */
      private static final long serialVersionUID = 1L;
  
      /**
       * FULL locale dependent date or time style.
       */
      public static final int FULL = DateFormat.FULL;
      /**
       * LONG locale dependent date or time style.
       */
      public static final int LONG = DateFormat.LONG;
      /**
       * MEDIUM locale dependent date or time style.
       */
      public static final int MEDIUM = DateFormat.MEDIUM;
      /**
       * SHORT locale dependent date or time style.
       */
      public static final int SHORT = DateFormat.SHORT;
  
      /**
       * The pattern.
       */
      private final String mPattern;
      /**
       * The time zone.
       */
      private final TimeZone mTimeZone;
      /**
       * The locale.
       */
      private final Locale mLocale;
      /**
       * The parsed rules.
       */
      private transient Rule[] mRules;
      /**
       * The estimated maximum length.
       */
      private transient int mMaxLengthEstimate;
  
      // Constructor
      //-----------------------------------------------------------------------
      /**
      * <p>Constructs a new FastDatePrinter.</p>
      * Use {@link FastDateFormat#getInstance(String, TimeZone, Locale)}  or another variation of the 
      * factory methods of {@link FastDateFormat} to get a cached FastDatePrinter instance.
      *
      * @param pattern  {@link java.text.SimpleDateFormat} compatible pattern
      * @param timeZone  non-null time zone to use
      * @param locale  non-null locale to use
      * @throws NullPointerException if pattern, timeZone, or locale is null.
      */
     protected FastDatePrinter(final String pattern, final TimeZone timeZone, final Locale locale) {
         mPattern = pattern;
         mTimeZone = timeZone;
         mLocale = locale;
 
         init();
     }
 
     /**
      * <p>Initializes the instance for first use.</p>
      */
     private void init() {
         final List<Rule> rulesList = parsePattern();
         mRules = rulesList.toArray(new Rule[rulesList.size()]);
 
         int len = 0;
         for (int i=mRules.length; --i >= 0; ) {
             len += mRules[i].estimateLength();
         }
 
         mMaxLengthEstimate = len;
     }
 
     // Parse the pattern
     //-----------------------------------------------------------------------
     /**
      * <p>Returns a list of Rules given a pattern.</p>
      *
      * @return a {@code List} of Rule objects
      * @throws IllegalArgumentException if pattern is invalid
      */
     protected List<Rule> parsePattern() {
         final DateFormatSymbols symbols = new DateFormatSymbols(mLocale);
         final List<Rule> rules = new ArrayList<Rule>();
 
         final String[] ERAs = symbols.getEras();
         final String[] months = symbols.getMonths();
         final String[] shortMonths = symbols.getShortMonths();
         final String[] weekdays = symbols.getWeekdays();
         final String[] shortWeekdays = symbols.getShortWeekdays();
         final String[] AmPmStrings = symbols.getAmPmStrings();
 
         final int length = mPattern.length();
         final int[] indexRef = new int[1];
 
         for (int i = 0; i < length; i++) {
             indexRef[0] = i;
             final String token = parseToken(mPattern, indexRef);
             i = indexRef[0];
 
             final int tokenLen = token.length();
             if (tokenLen == 0) {
                 break;
             }
 
             Rule rule;
             final char c = token.charAt(0);
 
             switch (c) {
             case 'G': // era designator (text)
                 rule = new TextField(Calendar.ERA, ERAs);
                 break;
             case 'y': // year (number)
                 if (tokenLen == 2) {
                     rule = TwoDigitYearField.INSTANCE;
                 } else {
                     rule = selectNumberRule(Calendar.YEAR, tokenLen < 4 ? 4 : tokenLen);
                 }
                 break;
             case 'M': // month in year (text and number)
                 if (tokenLen >= 4) {
                     rule = new TextField(Calendar.MONTH, months);
                 } else if (tokenLen == 3) {
                     rule = new TextField(Calendar.MONTH, shortMonths);
                 } else if (tokenLen == 2) {
                     rule = TwoDigitMonthField.INSTANCE;
                 } else {
                     rule = UnpaddedMonthField.INSTANCE;
                 }
                 break;
             case 'd': // day in month (number)
                 rule = selectNumberRule(Calendar.DAY_OF_MONTH, tokenLen);
                 break;
             case 'h': // hour in am/pm (number, 1..12)
                 rule = new TwelveHourField(selectNumberRule(Calendar.HOUR, tokenLen));
                 break;
             case 'H': // hour in day (number, 0..23)
                 rule = selectNumberRule(Calendar.HOUR_OF_DAY, tokenLen);
                 break;
             case 'm': // minute in hour (number)
                 rule = selectNumberRule(Calendar.MINUTE, tokenLen);
                 break;
             case 's': // second in minute (number)
                 rule = selectNumberRule(Calendar.SECOND, tokenLen);
                 break;
             case 'S': // millisecond (number)
                 rule = selectNumberRule(Calendar.MILLISECOND, tokenLen);
                 break;
             case 'E': // day in week (text)
                 rule = new TextField(Calendar.DAY_OF_WEEK, tokenLen < 4 ? shortWeekdays : weekdays);
                 break;
             case 'D': // day in year (number)
                 rule = selectNumberRule(Calendar.DAY_OF_YEAR, tokenLen);
                 break;
             case 'F': // day of week in month (number)
                 rule = selectNumberRule(Calendar.DAY_OF_WEEK_IN_MONTH, tokenLen);
                 break;
             case 'w': // week in year (number)
                 rule = selectNumberRule(Calendar.WEEK_OF_YEAR, tokenLen);
                 break;
             case 'W': // week in month (number)
                 rule = selectNumberRule(Calendar.WEEK_OF_MONTH, tokenLen);
                 break;
             case 'a': // am/pm marker (text)
                 rule = new TextField(Calendar.AM_PM, AmPmStrings);
                 break;
             case 'k': // hour in day (1..24)
                 rule = new TwentyFourHourField(selectNumberRule(Calendar.HOUR_OF_DAY, tokenLen));
                 break;
             case 'K': // hour in am/pm (0..11)
                 rule = selectNumberRule(Calendar.HOUR, tokenLen);
                 break;
             case 'X': // ISO 8601 
                 rule = Iso8601_Rule.getRule(tokenLen);
                 break;    
             case 'z': // time zone (text)
                 if (tokenLen >= 4) {
                     rule = new TimeZoneNameRule(mTimeZone, mLocale, TimeZone.LONG);
                 } else {
                     rule = new TimeZoneNameRule(mTimeZone, mLocale, TimeZone.SHORT);
                 }
                 break;
             case 'Z': // time zone (value)
                 if (tokenLen == 1) {
                     rule = TimeZoneNumberRule.INSTANCE_NO_COLON;
                 } else if (tokenLen == 2) {
                     rule = Iso8601_Rule.ISO8601_HOURS_COLON_MINUTES;
                 } else {
                     rule = TimeZoneNumberRule.INSTANCE_COLON;
                 }
                 break;
             case '\'': // literal text
                 final String sub = token.substring(1);
                 if (sub.length() == 1) {
                     rule = new CharacterLiteral(sub.charAt(0));
                 } else {
                     rule = new StringLiteral(sub);
                 }
                 break;
             default:
                 throw new IllegalArgumentException("Illegal pattern component: " + token);
             }
 
             rules.add(rule);
         }
 
         return rules;
     }
 
     /**
      * <p>Performs the parsing of tokens.</p>
      *
      * @param pattern  the pattern
      * @param indexRef  index references
      * @return parsed token
      */
     protected String parseToken(final String pattern, final int[] indexRef) {
         final StringBuilder buf = new StringBuilder();
 
         int i = indexRef[0];
         final int length = pattern.length();
 
         char c = pattern.charAt(i);
         if (c >= 'A' && c <= 'Z' || c >= 'a' && c <= 'z') {
             // Scan a run of the same character, which indicates a time
             // pattern.
             buf.append(c);
 
             while (i + 1 < length) {
                 final char peek = pattern.charAt(i + 1);
                 if (peek == c) {
                     buf.append(c);
                     i++;
                 } else {
                     break;
                 }
             }
         } else {
             // This will identify token as text.
             buf.append('\'');
 
             boolean inLiteral = false;
 
             for (; i < length; i++) {
                 c = pattern.charAt(i);
 
                 if (c == '\'') {
                     if (i + 1 < length && pattern.charAt(i + 1) == '\'') {
                         // '' is treated as escaped '
                         i++;
                         buf.append(c);
                     } else {
                         inLiteral = !inLiteral;
                     }
                 } else if (!inLiteral &&
                          (c >= 'A' && c <= 'Z' || c >= 'a' && c <= 'z')) {
                     i--;
                     break;
                 } else {
                     buf.append(c);
                 }
             }
         }
 
         indexRef[0] = i;
         return buf.toString();
     }
 
     /**
      * <p>Gets an appropriate rule for the padding required.</p>
      *
      * @param field  the field to get a rule for
      * @param padding  the padding required
      * @return a new rule with the correct padding
      */
     protected NumberRule selectNumberRule(final int field, final int padding) {
         switch (padding) {
         case 1:
             return new UnpaddedNumberField(field);
         case 2:
             return new TwoDigitNumberField(field);
         default:
             return new PaddedNumberField(field, padding);
         }
     }
 
     // Format methods
     //-----------------------------------------------------------------------
     /**
      * <p>Formats a {@code Date}, {@code Calendar} or
      * {@code Long} (milliseconds) object.</p>
      *
      * @param obj  the object to format
      * @param toAppendTo  the buffer to append to
      * @param pos  the position - ignored
      * @return the buffer passed in
      */
     @Override
     public StringBuilder format(final Object obj, final StringBuilder toAppendTo, final FieldPosition pos) {
         if (obj instanceof Date) {
             return format((Date) obj, toAppendTo);
         } else if (obj instanceof Calendar) {
             return format((Calendar) obj, toAppendTo);
         } else if (obj instanceof Long) {
             return format(((Long) obj).longValue(), toAppendTo);
         } else {
             throw new IllegalArgumentException("Unknown class: " +
                 (obj == null ? "<null>" : obj.getClass().getName()));
         }
     }
 
     /* (non-Javadoc)
      * @see org.apache.commons.lang3.time.DatePrinter#format(long)
      */
     @Override
     public String format(final long millis) {
         final Calendar c = newCalendar();  // hard code GregorianCalendar
         c.setTimeInMillis(millis);
         return applyRulesToString(c);
     }
 
     /**
      * Creates a String representation of the given Calendar by applying the rules of this printer to it.
      * @param c the Calender to apply the rules to.
      * @return a String representation of the given Calendar.
      */
     private String applyRulesToString(final Calendar c) {
         return applyRules(c, new StringBuilder(mMaxLengthEstimate)).toString();
     }
 
     /**
      * Creation method for ne calender instances.
      * @return a new Calendar instance.
      */
     private GregorianCalendar newCalendar() {
         // hard code GregorianCalendar
         return new GregorianCalendar(mTimeZone, mLocale);
     }
 
     /* (non-Javadoc)
      * @see org.apache.commons.lang3.time.DatePrinter#format(java.util.Date)
      */
     @Override
     public String format(final Date date) {
         final Calendar c = newCalendar();  // hard code GregorianCalendar
         c.setTime(date);
         return applyRulesToString(c);
     }
 
     /* (non-Javadoc)
      * @see org.apache.commons.lang3.time.DatePrinter#format(java.util.Calendar)
      */
     @Override
     public String format(final Calendar calendar) {
         return format(calendar, new StringBuilder(mMaxLengthEstimate)).toString();
     }
 
     /* (non-Javadoc)
      * @see org.apache.commons.lang3.time.DatePrinter#format(long, java.lang.StringBuilder)
      */
     @Override
     public StringBuilder format(final long millis, final StringBuilder buf) {
         return format(new Date(millis), buf);
     }
 
     /* (non-Javadoc)
      * @see org.apache.commons.lang3.time.DatePrinter#format(java.util.Date, java.lang.StringBuilder)
      */
     @Override
     public StringBuilder format(final Date date, final StringBuilder buf) {
         final Calendar c = newCalendar();  // hard code GregorianCalendar
         c.setTime(date);
         return applyRules(c, buf);
     }
 
     /* (non-Javadoc)
      * @see org.apache.commons.lang3.time.DatePrinter#format(java.util.Calendar, java.lang.StringBuilder)
      */
     @Override
     public StringBuilder format(final Calendar calendar, final StringBuilder buf) {
         // do not pass in calendar directly, this will cause TimeZone of FastDatePrinter to be ignored
         return format(calendar.getTime(), buf);
     }
 
     /**
      * <p>Performs the formatting by applying the rules to the
      * specified calendar.</p>
      *
      * @param calendar  the calendar to format
      * @param buf  the buffer to format into
      * @return the specified string buffer
      */
     protected StringBuilder applyRules(final Calendar calendar, final StringBuilder buf) {
         for (final Rule rule : mRules) {
             rule.appendTo(buf, calendar);
         }
         return buf;
     }
 
     // Accessors
     //-----------------------------------------------------------------------
     /* (non-Javadoc)
      * @see org.apache.commons.lang3.time.DatePrinter#getPattern()
      */
     @Override
     public String getPattern() {
         return mPattern;
     }
 
     /* (non-Javadoc)
      * @see org.apache.commons.lang3.time.DatePrinter#getTimeZone()
      */
     @Override
     public TimeZone getTimeZone() {
         return mTimeZone;
     }
 
     /* (non-Javadoc)
      * @see org.apache.commons.lang3.time.DatePrinter#getLocale()
      */
     @Override
     public Locale getLocale() {
         return mLocale;
     }
 
     /**
      * <p>Gets an estimate for the maximum string length that the
      * formatter will produce.</p>
      *
      * <p>The actual formatted length will almost always be less than or
      * equal to this amount.</p>
      *
      * @return the maximum formatted length
      */
     public int getMaxLengthEstimate() {
         return mMaxLengthEstimate;
     }
 
     // Basics
     //-----------------------------------------------------------------------
     /**
      * <p>Compares two objects for equality.</p>
      *
      * @param obj  the object to compare to
      * @return {@code true} if equal
      */
     @Override
     public boolean equals(final Object obj) {
         if (obj instanceof FastDatePrinter == false) {
             return false;
         }
         final FastDatePrinter other = (FastDatePrinter) obj;
         return mPattern.equals(other.mPattern)
             && mTimeZone.equals(other.mTimeZone) 
             && mLocale.equals(other.mLocale);
     }
 
     /**
      * <p>Returns a hashcode compatible with equals.</p>
      *
      * @return a hashcode compatible with equals
      */
     @Override
     public int hashCode() {
         return mPattern.hashCode() + 13 * (mTimeZone.hashCode() + 13 * mLocale.hashCode());
     }
 
     /**
      * <p>Gets a debugging string version of this formatter.</p>
      *
      * @return a debugging string
      */
     @Override
     public String toString() {
         return "FastDatePrinter[" + mPattern + "," + mLocale + "," + mTimeZone.getID() + "]";
     }
 
     // Serializing
     //-----------------------------------------------------------------------
     /**
      * Create 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();
         init();
     }
 
     /**
      * Appends digits to the given buffer.
      * 
      * @param buffer the buffer to append to.
      * @param value the value to append digits from.
      */
     private static void appendDigits(final StringBuilder buffer, final int value) {
         buffer.append((char)(value / 10 + '0'));
         buffer.append((char)(value % 10 + '0'));
     }
 
     // Rules
     //-----------------------------------------------------------------------
     /**
      * <p>Inner class defining a rule.</p>
      */
     private interface Rule {
         /**
          * Returns the estimated length of the result.
          *
          * @return the estimated length
          */
         int estimateLength();
 
         /**
          * Appends the value of the specified calendar to the output buffer based on the rule implementation.
          *
          * @param buffer the output buffer
          * @param calendar calendar to be appended
          */
         void appendTo(StringBuilder buffer, Calendar calendar);
     }
 
     /**
      * <p>Inner class defining a numeric rule.</p>
      */
     private interface NumberRule extends Rule {
         /**
          * Appends the specified value to the output buffer based on the rule implementation.
          *
          * @param buffer the output buffer
          * @param value the value to be appended
          */
         void appendTo(StringBuilder buffer, int value);
     }
 
     /**
      * <p>Inner class to output a constant single character.</p>
      */
     private static class CharacterLiteral implements Rule {
         private final char mValue;
 
         /**
          * Constructs a new instance of {@code CharacterLiteral}
          * to hold the specified value.
          *
          * @param value the character literal
          */
         CharacterLiteral(final char value) {
             mValue = value;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return 1;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             buffer.append(mValue);
         }
     }
 
     /**
      * <p>Inner class to output a constant string.</p>
      */
     private static class StringLiteral implements Rule {
         private final String mValue;
 
         /**
          * Constructs a new instance of {@code StringLiteral}
          * to hold the specified value.
          *
          * @param value the string literal
          */
         StringLiteral(final String value) {
             mValue = value;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return mValue.length();
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             buffer.append(mValue);
         }
     }
 
     /**
      * <p>Inner class to output one of a set of values.</p>
      */
     private static class TextField implements Rule {
         private final int mField;
         private final String[] mValues;
 
         /**
          * Constructs an instance of {@code TextField}
          * with the specified field and values.
          *
          * @param field the field
          * @param values the field values
          */
         TextField(final int field, final String[] values) {
             mField = field;
             mValues = values;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             int max = 0;
             for (int i=mValues.length; --i >= 0; ) {
                 final int len = mValues[i].length();
                 if (len > max) {
                     max = len;
                 }
             }
             return max;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             buffer.append(mValues[calendar.get(mField)]);
         }
     }
 
     /**
      * <p>Inner class to output an unpadded number.</p>
      */
     private static class UnpaddedNumberField implements NumberRule {
         private final int mField;
 
         /**
          * Constructs an instance of {@code UnpadedNumberField} with the specified field.
          *
          * @param field the field
          */
         UnpaddedNumberField(final int field) {
             mField = field;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return 4;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             appendTo(buffer, calendar.get(mField));
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public final void appendTo(final StringBuilder buffer, final int value) {
             if (value < 10) {
                 buffer.append((char)(value + '0'));
             } else if (value < 100) {
                 appendDigits(buffer, value);
             } else {
                 buffer.append(value);
             }
         }
     }
 
     /**
      * <p>Inner class to output an unpadded month.</p>
      */
     private static class UnpaddedMonthField implements NumberRule {
         static final UnpaddedMonthField INSTANCE = new UnpaddedMonthField();
 
         /**
          * Constructs an instance of {@code UnpaddedMonthField}.
          *
          */
         UnpaddedMonthField() {
             super();
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return 2;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             appendTo(buffer, calendar.get(Calendar.MONTH) + 1);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public final void appendTo(final StringBuilder buffer, final int value) {
             if (value < 10) {
                 buffer.append((char)(value + '0'));
             } else {
                 appendDigits(buffer, value);
             }
         }
     }
 
     /**
      * <p>Inner class to output a padded number.</p>
      */
     private static class PaddedNumberField implements NumberRule {
         private final int mField;
         private final int mSize;
 
         /**
          * Constructs an instance of {@code PaddedNumberField}.
          *
          * @param field the field
          * @param size size of the output field
          */
         PaddedNumberField(final int field, final int size) {
             if (size < 3) {
                 // Should use UnpaddedNumberField or TwoDigitNumberField.
                 throw new IllegalArgumentException();
             }
             mField = field;
             mSize = size;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return mSize;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             appendTo(buffer, calendar.get(mField));
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public final void appendTo(final StringBuilder buffer, int value) {
             // pad the buffer with adequate zeros
             for(int digit = 0; digit<mSize; ++digit) {
                 buffer.append('0');                
             }
             // backfill the buffer with non-zero digits
             int index = buffer.length();
             for( ; value>0; value /= 10) {
                 buffer.setCharAt(--index, (char)('0' + value % 10));
             }
         }
     }
 
     /**
      * <p>Inner class to output a two digit number.</p>
      */
     private static class TwoDigitNumberField implements NumberRule {
         private final int mField;
 
         /**
          * Constructs an instance of {@code TwoDigitNumberField} with the specified field.
          *
          * @param field the field
          */
         TwoDigitNumberField(final int field) {
             mField = field;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return 2;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             appendTo(buffer, calendar.get(mField));
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public final void appendTo(final StringBuilder buffer, final int value) {
             if (value < 100) {
                 appendDigits(buffer, value);
             } else {
                 buffer.append(value);
             }
         }
     }
 
     /**
      * <p>Inner class to output a two digit year.</p>
      */
     private static class TwoDigitYearField implements NumberRule {
         static final TwoDigitYearField INSTANCE = new TwoDigitYearField();
 
         /**
          * Constructs an instance of {@code TwoDigitYearField}.
          */
         TwoDigitYearField() {
             super();
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return 2;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             appendTo(buffer, calendar.get(Calendar.YEAR) % 100);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public final void appendTo(final StringBuilder buffer, final int value) {
             appendDigits(buffer, value);
         }
     }
 
     /**
      * <p>Inner class to output a two digit month.</p>
      */
     private static class TwoDigitMonthField implements NumberRule {
         static final TwoDigitMonthField INSTANCE = new TwoDigitMonthField();
 
         /**
          * Constructs an instance of {@code TwoDigitMonthField}.
          */
         TwoDigitMonthField() {
             super();
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return 2;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             appendTo(buffer, calendar.get(Calendar.MONTH) + 1);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public final void appendTo(final StringBuilder buffer, final int value) {
             appendDigits(buffer, value);
         }
     }
 
     /**
      * <p>Inner class to output the twelve hour field.</p>
      */
     private static class TwelveHourField implements NumberRule {
         private final NumberRule mRule;
 
         /**
          * Constructs an instance of {@code TwelveHourField} with the specified
          * {@code NumberRule}.
          *
          * @param rule the rule
          */
         TwelveHourField(final NumberRule rule) {
             mRule = rule;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return mRule.estimateLength();
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             int value = calendar.get(Calendar.HOUR);
             if (value == 0) {
                 value = calendar.getLeastMaximum(Calendar.HOUR) + 1;
             }
             mRule.appendTo(buffer, value);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final int value) {
             mRule.appendTo(buffer, value);
         }
     }
 
     /**
      * <p>Inner class to output the twenty four hour field.</p>
      */
     private static class TwentyFourHourField implements NumberRule {
         private final NumberRule mRule;
 
         /**
          * Constructs an instance of {@code TwentyFourHourField} with the specified
          * {@code NumberRule}.
          *
          * @param rule the rule
          */
         TwentyFourHourField(final NumberRule rule) {
             mRule = rule;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return mRule.estimateLength();
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             int value = calendar.get(Calendar.HOUR_OF_DAY);
             if (value == 0) {
                 value = calendar.getMaximum(Calendar.HOUR_OF_DAY) + 1;
             }
             mRule.appendTo(buffer, value);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final int value) {
             mRule.appendTo(buffer, value);
         }
     }
 
     //-----------------------------------------------------------------------
 
     private static final ConcurrentMap<TimeZoneDisplayKey, String> cTimeZoneDisplayCache =
         new ConcurrentHashMap<TimeZoneDisplayKey, String>(7);
     /**
      * <p>Gets the time zone display name, using a cache for performance.</p>
      *
      * @param tz  the zone to query
      * @param daylight  true if daylight savings
      * @param style  the style to use {@code TimeZone.LONG} or {@code TimeZone.SHORT}
      * @param locale  the locale to use
      * @return the textual name of the time zone
      */
     static String getTimeZoneDisplay(final TimeZone tz, final boolean daylight, final int style, final Locale locale) {
         final TimeZoneDisplayKey key = new TimeZoneDisplayKey(tz, daylight, style, locale);
         String value = cTimeZoneDisplayCache.get(key);
         if (value == null) {
             // This is a very slow call, so cache the results.
             value = tz.getDisplayName(daylight, style, locale);
             final String prior = cTimeZoneDisplayCache.putIfAbsent(key, value);
             if (prior != null) {
                 value= prior;
             }
         }
         return value;
     }
 
     /**
      * <p>Inner class to output a time zone name.</p>
      */
     private static class TimeZoneNameRule implements Rule {
         private final Locale mLocale;
         private final int mStyle;
         private final String mStandard;
         private final String mDaylight;
 
         /**
          * Constructs an instance of {@code TimeZoneNameRule} with the specified properties.
          *
          * @param timeZone the time zone
          * @param locale the locale
          * @param style the style
          */
         TimeZoneNameRule(final TimeZone timeZone, final Locale locale, final int style) {
             mLocale = locale;
             mStyle = style;
             
             mStandard = getTimeZoneDisplay(timeZone, false, style, locale);
             mDaylight = getTimeZoneDisplay(timeZone, true, style, locale);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             // We have no access to the Calendar object that will be passed to
             // appendTo so base estimate on the TimeZone passed to the
             // constructor
             return Math.max(mStandard.length(), mDaylight.length());
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             final TimeZone zone = calendar.getTimeZone();
             if (calendar.get(Calendar.DST_OFFSET) != 0) {
                 buffer.append(getTimeZoneDisplay(zone, true, mStyle, mLocale));
             } else {
                 buffer.append(getTimeZoneDisplay(zone, false, mStyle, mLocale));
             }
         }
     }
 
     /**
      * <p>Inner class to output a time zone as a number {@code +/-HHMM}
      * or {@code +/-HH:MM}.</p>
      */
     private static class TimeZoneNumberRule implements Rule {
         static final TimeZoneNumberRule INSTANCE_COLON = new TimeZoneNumberRule(true);
         static final TimeZoneNumberRule INSTANCE_NO_COLON = new TimeZoneNumberRule(false);
         
         final boolean mColon;
 
         /**
          * Constructs an instance of {@code TimeZoneNumberRule} with the specified properties.
          *
          * @param colon add colon between HH and MM in the output if {@code true}
          */
         TimeZoneNumberRule(final boolean colon) {
             mColon = colon;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return 5;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             
             int offset = calendar.get(Calendar.ZONE_OFFSET) + calendar.get(Calendar.DST_OFFSET);
 
             if (offset < 0) {
                 buffer.append('-');
                 offset = -offset;
             } else {
                 buffer.append('+');
             }
 
             final int hours = offset / (60 * 60 * 1000);
             appendDigits(buffer, hours);
 
             if (mColon) {
                 buffer.append(':');
             }
 
             final int minutes = offset / (60 * 1000) - 60 * hours;
             appendDigits(buffer, minutes);
         }
     }
 
     /**
      * <p>Inner class to output a time zone as a number {@code +/-HHMM}
      * or {@code +/-HH:MM}.</p>
      */
     private static class Iso8601_Rule implements Rule {
         
         // Sign TwoDigitHours or Z
         static final Iso8601_Rule ISO8601_HOURS = new Iso8601_Rule(3);       
         // Sign TwoDigitHours Minutes or Z
         static final Iso8601_Rule ISO8601_HOURS_MINUTES = new Iso8601_Rule(5);
         // Sign TwoDigitHours : Minutes or Z
         static final Iso8601_Rule ISO8601_HOURS_COLON_MINUTES = new Iso8601_Rule(6);
 
         /**
          * Factory method for Iso8601_Rules.
          *
          * @param tokenLen a token indicating the length of the TimeZone String to be formatted.
          * @return a Iso8601_Rule that can format TimeZone String of length {@code tokenLen}. If no such
          *          rule exists, an IllegalArgumentException will be thrown.
          */
         static Iso8601_Rule getRule(final int tokenLen) {
             switch(tokenLen) {
             case 1:
                 return Iso8601_Rule.ISO8601_HOURS;
             case 2:
                 return Iso8601_Rule.ISO8601_HOURS_MINUTES;
             case 3:
                 return Iso8601_Rule.ISO8601_HOURS_COLON_MINUTES;
             default:
                 throw new IllegalArgumentException("invalid number of X");                    
             }
         }        
         
         final int length;
 
         /**
          * Constructs an instance of {@code Iso8601_Rule} with the specified properties.
          *
          * @param length The number of characters in output (unless Z is output)
          */
         Iso8601_Rule(final int length) {
             this.length = length;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int estimateLength() {
             return length;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void appendTo(final StringBuilder buffer, final Calendar calendar) {
             int offset = calendar.get(Calendar.ZONE_OFFSET) + calendar.get(Calendar.DST_OFFSET);
             if (offset == 0) {
                 buffer.append("Z");
                 return;
             }
             
             if (offset < 0) {
                 buffer.append('-');
                 offset = -offset;
             } else {
                 buffer.append('+');
             }
 
             final int hours = offset / (60 * 60 * 1000);
             appendDigits(buffer, hours);
 
             if (length<5) {
                 return;
             }
             
             if (length==6) {
                 buffer.append(':');
             }
 
             final int minutes = offset / (60 * 1000) - 60 * hours;
             appendDigits(buffer, minutes);
         }
     }
 
     // ----------------------------------------------------------------------
     /**
      * <p>Inner class that acts as a compound key for time zone names.</p>
      */
     private static class TimeZoneDisplayKey {
         private final TimeZone mTimeZone;
         private final int mStyle;
         private final Locale mLocale;
 
         /**
          * Constructs an instance of {@code TimeZoneDisplayKey} with the specified properties.
          *
          * @param timeZone the time zone
          * @param daylight adjust the style for daylight saving time if {@code true}
          * @param style the timezone style
          * @param locale the timezone locale
          */
         TimeZoneDisplayKey(final TimeZone timeZone,
                            final boolean daylight, final int style, final Locale locale) {
             mTimeZone = timeZone;
             if (daylight) {
                 mStyle = style | 0x80000000;
             } else {
                 mStyle = style;
             }
             mLocale = locale;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int hashCode() {
             return (mStyle * 31 + mLocale.hashCode() ) * 31 + mTimeZone.hashCode();
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public boolean equals(final Object obj) {
             if (this == obj) {
                 return true;
             }
             if (obj instanceof TimeZoneDisplayKey) {
                 final TimeZoneDisplayKey other = (TimeZoneDisplayKey)obj;
                 return
                     mTimeZone.equals(other.mTimeZone) &&
                     mStyle == other.mStyle &&
                     mLocale.equals(other.mLocale);
             }
             return false;
         }
     }
 }