Incomplete -Rebirth-

Java Pretty Date

John Resig の記事のJavaScriptを移植した、ISO8601:2004の日付をParseするけれども、 commons-langを使うのが素直。

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

//import org.apache.commons.lang.time.DateFormatUtils

public class PrettyDate {
    public static String prettyDate(String dateString) throws ParseException {
        if (dateString == null)
            return null;

        // Date date = DateFormatUtils.ISO_DATETIME_TIME_ZONE_FORMAT.format(date);
        Date date = parse(dateString);
        return prettyDate(date);

    }

    public static String prettyDate(Date date) throws ParseException {
        if (date == null) return null;
        Calendar cal = Calendar.getInstance();
        long diff = (cal.getTime().getTime() - date.getTime()) / 1000;
        double dayDiff = Math.floor(diff / 86400);

        if (dayDiff < 0 || dayDiff >= 31)
            return null;

        if (dayDiff == 0) {
            if (diff < 60   ) return "just now";
            if (diff < 120  ) return "1 minute ago";
            if (diff < 3600 ) return (int) Math.floor(diff / 60) + " minutes ago";
            if (diff < 7200 ) return "1 hour ago";
            if (diff < 86400) return (int) Math.floor(diff / 3600) + " hours ago";
        } else if (dayDiff == 1) {
            return "Yesterday";
        } else if (dayDiff < 7) {
            return (int) dayDiff + " days ago";
        } else if (dayDiff < 31) {
            return (int) Math.ceil(dayDiff / 7) + " weeks ago";
        }
        return null;

    }

    private static final SimpleDateFormat DATE_FORMAT_MILLIS_ISO8601 
            = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
    private static final String        REGEX_DATE_FORMAT_MILLIS_ISO8601 
    = "\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}\\.\\d{3}[-+]\\d{2}:\\d{2}";

    public static Date parse(String dateString) throws ParseException {
        Date date = null;
        if (dateString.matches(REGEX_DATE_FORMAT_MILLIS_ISO8601)) {
            int index = dateString.lastIndexOf(":");
            StringBuffer sb = new StringBuffer(dateString).deleteCharAt(index);
            date = DATE_FORMAT_MILLIS_ISO8601.parse(sb.toString());
        }
        return date;
    }

    public static void main(String[] args) {
        String[] dateStrings = { "2008-01-29T20:38:17.123+09:00",
                "2008-01-29T20:28:17.123+09:00",
                "2008-01-29T10:28:17.123+09:00",
                "2008-01-28T10:28:17.123+09:00",
                "2008-01-25T10:28:17.123+09:00",
                "2008-01-20T10:28:17.123+09:00", };
        try {
            for (String dateString : dateStrings) {
                System.out.println(PrettyDate.prettyDate(dateString));
            }
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

以下実行結果

prettyDate("2008-01-29T20:38:17.123+09:00")// =>21 minutes ago
prettyDate("2008-01-29T20:28:17.123+09:00")// =>31 minutes ago
prettyDate("2008-01-29T10:28:17.123+09:00")// =>10 hours ago
prettyDate("2008-01-28T10:28:17.123+09:00")// =>Yesterday
prettyDate("2008-01-25T10:28:17.123+09:00")// =>4 days ago
prettyDate("2008-01-20T10:28:17.123+09:00")// =>2 weeks ago

A quick preview will be rendered here when you click "Preview" button.