SimpleDateFormat.java

package edu.fresno.gwt.vehiclereservation.shared;

import java.io.Serializable;
import java.util.Arrays;
import java.util.Date;
import java.util.List;

/**
 * <dl>
 * <dt><b>Title: </b><dd>SimpleDateFormat</dd>
 * <p>
 * <dt><b>Description: </b><dd>GWT does not implement any of the java.text package, so this class tries to fill the void
 * of the missing java.text.SimpleDateFormat class. This version however only supports a subset of the date and time patterns
 * supported by its java.text counterpart. The pattern symbols supported by this class are:
 * <dl>
 * <dt><b>E</b></dt><dd>Day in a week</dd>
 * <dt><b>d</b></dt><dd>Day of the month</dd>
 * <dt><b>y</b></dt><dd>Year</dd>
 * <dt><b>M</b></dt><dd>Month January, Jan, 01, 1</dd>
 * <dt><b>H</b></dt><dd>Hour in 24 hour format (0-23)</dd>
 * <dt><b>h</b></dt><dd>Hour in 12 hour format (1-12)</dd>
 * <dt><b>m</b></dt><dd>Minute of the hour </dd>
 * <dt><b>s</b></dt><dd>Seconds of the minute</dd>
 * <dt><b>a</b></dt><dd>am/pm</dd>
 * </dl>
 * All characters that are not recognised as a date format character are translated literally into the output string. <br/>
 * </dd>
 * <p>
 * </dl>
 * @author <a href="mailto:jas...@greenrivercomputing.com">Jason Essington</a>
 * @version $Revision: 0.0 $
 */

public class SimpleDateFormat implements Serializable
{
   private static final String TOKEN_DAY_OF_WEEK = "E";
   private static final String TOKEN_DAY_OF_MONTH = "d";
   private static final String TOKEN_MONTH = "M";
   private static final String TOKEN_YEAR = "y";
   private static final String TOKEN_HOUR_12 = "h";
   private static final String TOKEN_HOUR_24 = "H";
   private static final String TOKEN_MINUTE = "m";
   private static final String TOKEN_SECOND = "s";
   private static final String TOKEN_AM_PM = "a";

   private static final String AM = "AM";
   private static final String PM = "PM";

   private static final List<String> SUPPORTED_DF_TOKENS = Arrays.asList(new String[] { TOKEN_DAY_OF_WEEK, TOKEN_DAY_OF_MONTH,
         TOKEN_MONTH, TOKEN_YEAR, TOKEN_HOUR_12, TOKEN_HOUR_24, TOKEN_MINUTE, TOKEN_SECOND, TOKEN_AM_PM });

   private static final String[] MONTH_LONG = { "January", "February", "March", "April", "May", "June", "July",
         "August", "September", "October", "November", "December" };

   private static final String[] MONTH_SHORT = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sept", "Oct",
         "Nov", "Dec" };

   private static final String[] WEEKDAY_LONG = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday",
         "Saturday" };

   private static final String[] WEEKDAY_SHORT = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };

   private String format;

   public SimpleDateFormat(String pattern)
   {
      format = pattern;
   }

   public String format(Date date)
   {
      String f = "";
      if (format != null && format.length() > 0)
      {
         String lastTokenType = null;
         String currentToken = "";
         for (int i = 0; i < format.length(); i++)
         {
            String thisChar = format.substring(i, i + 1);
            String currentTokenType = SUPPORTED_DF_TOKENS.contains(thisChar) ? thisChar : "";

            if (currentTokenType.equals(lastTokenType) || i == 0)
            {
               currentToken += thisChar;
               lastTokenType = currentTokenType;
            }
            else
            {
               if ("".equals(lastTokenType))
                  f += currentToken;
               else
                  f += handleToken(currentToken, date);

               currentToken = thisChar;
               lastTokenType = currentTokenType;
            }
         }
         if ("".equals(lastTokenType))
            f += currentToken;
         else
            f += handleToken(currentToken, date);
      }

      return f;
   }

   /**
    * takes a date format string and returns the formatted portion of the date. For instance if the token is MMMM then
    * the full month name is returned.
    * @param token date format token
    * @param date date to format
    * @return formatted portion of the date
    */
   @SuppressWarnings("deprecation")
   private String handleToken(String token, Date date)
   {
      String response = token;
      String tc = token.substring(0, 1);
      if (TOKEN_DAY_OF_WEEK.equals(tc))
      {
         if (token.length() > 3)
            response = WEEKDAY_LONG[date.getDay()];
         else
            response = WEEKDAY_SHORT[date.getDay()];
      }
      else if (TOKEN_DAY_OF_MONTH.equals(tc))
      {
         if (token.length() == 1)
            response = Integer.toString(date.getDate());
         else
            response = twoCharDateField(date.getDate());
      }
      else if (TOKEN_MONTH.equals(tc))
      {
         switch (token.length())
         {
            case 1:
               response = Integer.toString(date.getMonth());
               break;
            case 2:
               response = twoCharDateField(date.getMonth());
               break;
            case 3:
               response = MONTH_SHORT[date.getMonth()];
               break;
            default:
               response = MONTH_LONG[date.getMonth()];
               break;
         }
      }
      else if (TOKEN_YEAR.equals(tc))
      {
         if (token.length() > 2)
            response = Integer.toString(date.getYear() + 1900);
         else
            response = twoCharDateField(date.getYear());
      }
      else if (TOKEN_HOUR_12.equals(tc))
      {
         int h = date.getHours();
         if (h == 0)
            h = 12;
         else if (h > 12) h -= 12;

         if (token.length() > 1)
            response = twoCharDateField(h);
         else
            response = Integer.toString(h);
      }
      else if (TOKEN_HOUR_24.equals(tc))
      {
         if (token.length() > 1)
            response = twoCharDateField(date.getHours());
         else
            response = Integer.toString(date.getHours());
      }
      else if (TOKEN_MINUTE.equals(tc))
      {
         if (token.length() > 1)
            response = twoCharDateField(date.getMinutes());
         else
            response = Integer.toString(date.getMinutes());
      }
      else if (TOKEN_SECOND.equals(tc))
      {
         if (token.length() > 1)
            response = twoCharDateField(date.getSeconds());
         else
            response = Integer.toString(date.getSeconds());
      }
      else if (TOKEN_AM_PM.equals(tc))
      {
         int hour = date.getHours();
         if (hour > 11)
            response = PM;
         else
            response = AM;
      }

      return response;

   }

   /**
    * This is basically just a sneaky way to guarantee that our 1 or 2 digit numbers come out as a 2 character string.
    * we add an arbitrary number larger than 100, convert this new number to a string, then take the right most 2 characters.
    * @param num
    * @return
    */
   private String twoCharDateField(int num)
   {
      String res = Integer.toString(num + 1900);
      res = res.substring(res.length() - 2);
      return res;
   }
}