# Dates.java

    /*
     * Copyright 2009 Niclas Hedhman.
     *
     * Licensed  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.qi4j.api.util;

    import java.text.DateFormat;
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    import java.util.TimeZone;

    /**
     * Useful methods for handling Dates.
     */
    public final class Dates
    {
        // Formatters are not thread-safe. Create one per thread
        private static final ThreadLocal<DateFormat> ISO8601 = new ThreadLocal<DateFormat>()
        {
            @Override
            protected DateFormat initialValue()
            {
                return new SimpleDateFormat( "yyyy-MM-dd'T'HH:mm:ss.SSSZ" );
            }
        };

        private static final ThreadLocal<DateFormat> ISO8601_UTC = new ThreadLocal<DateFormat>()
        {
            @Override
            protected DateFormat initialValue()
            {
                SimpleDateFormat dateFormat = new SimpleDateFormat( "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'" );
                dateFormat.setTimeZone( TimeZone.getTimeZone( "UTC" ) );
                return dateFormat;
            }
        };

        /**
         * @param stringDate a string representing a date as either ISO8601, @millis@ or /Date() formats
         * @return a Date
         */
        public static Date fromString( String stringDate )
        {
            try
            {
                Date date = ISO8601_UTC.get().parse( stringDate );
                return date;
            }
            catch( ParseException e )
            {
                try
                {
                    Date date = ISO8601.get().parse( stringDate );
                    return date;
                }
                catch( ParseException e1 )
                {
                    // @millis@ format
                    if( stringDate.startsWith( "@" ) && stringDate.endsWith( "@" ) )
                    {
                        long time = Long.parseLong( stringDate.substring( 1, stringDate.length() - 1 ) );
                        Date date = new Date( time );
                        return date;
                    }
                    else if( stringDate.startsWith( "/Date(" ) && stringDate.endsWith( ")/" ) ) // Microsoft format
                    {
                        long time = Long.parseLong( stringDate.substring( 6, stringDate.length() - 2 ) );
                        Date date = new Date( time );
                        return date;
                    }
                    throw new IllegalStateException( "Illegal date:" + stringDate );
                }
            }
        }

        /**
         * @param date a Date
         * @return String representation in ISO8601 UTC
         */
        public static String toUtcString( Date date )
        {
            return ISO8601_UTC.get().format( date );
        }

        private Dates()
        {
        }
    }