利用ICU解决日期格式国际化问题

ICU jar包下载地址：http://apps.icu-project.org/icu-jsp/downloadPage.jsp?ver=51.2&base=j&svn=release-51-2

日期格式间的相互转换：

import java.text.FieldPosition;import java.text.ParseException;import java.util.Calendar;import java.util.Date;import java.util.Locale;import com.ibm.icu.text.DateFormat;public class dataformat {    public void run() {        // Formatting Dates        DateFormat dfUS = DateFormat.getDateInstance(DateFormat.FULL, Locale.US);        DateFormat dfFrance = DateFormat.getDateInstance(DateFormat.FULL, Locale.FRANCE);        Calendar c = Calendar.getInstance();        Date d = c.getTime();                StringBuffer sb = new StringBuffer();        sb = dfUS.format(d, sb, new FieldPosition(0));        System.out.println(sb.toString());        StringBuffer sbf = new StringBuffer();        sbf = dfFrance.format(d, sbf, new FieldPosition(0));        System.out.println(sbf.toString());        StringBuffer sbg = new StringBuffer();        DateFormat dfg = DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.SHORT);        FieldPosition pos = new FieldPosition(DateFormat.MINUTE_FIELD);        sbg = dfg.format(d, sbg, pos);        System.out.println(sbg.toString());        System.out.println(sbg.toString().substring(pos.getBeginIndex(), pos.getEndIndex()));        // Parsing Dates        String dateString_US = "Thursday, February 7, 2008";        String dateString_FRANCE = "jeudi 7 février 2008";        try {            Date parsedDate_US = dfUS.parse(dateString_US);            Date parsedDate_FRANCE = dfFrance.parse(dateString_FRANCE);            System.out.println(parsedDate_US.toString());            System.out.println(parsedDate_FRANCE.toString());        } catch (ParseException pe) {            System.out.println("Exception while parsing :" + pe);        }    }    public static void main(String args[]) {        new dataformat().run();    }}

日期格式转换为各个国家的日期格式时主要使用了format函数（最终调用了Calendar的setTime函数）：

    /**     * Formats a time object into a time string. Examples of time objects     * are a time value expressed in milliseconds and a Date object.     * @param obj must be a Number or a Date or a Calendar.     * @param toAppendTo the string buffer for the returning time string.     * @return the formatted time string.     * @param fieldPosition keeps track of the position of the field     * within the returned string.     * On input: an alignment field,     * if desired. On output: the offsets of the alignment field. For     * example, given a time text "1996.07.10 AD at 15:08:56 PDT",     * if the given fieldPosition is DateFormat.YEAR_FIELD, the     * begin index and end index of fieldPosition will be set to     * 0 and 4, respectively.     * Notice that if the same time field appears     * more than once in a pattern, the fieldPosition will be set for the first     * occurrence of that time field. For instance, formatting a Date to     * the time string "1 PM PDT (Pacific Daylight Time)" using the pattern     * "h a z (zzzz)" and the alignment field DateFormat.TIMEZONE_FIELD,     * the begin index and end index of fieldPosition will be set to     * 5 and 8, respectively, for the first occurrence of the timezone     * pattern character 'z'.     * @see java.text.Format     * @stable ICU 2.0     */    public final StringBuffer format(Object obj, StringBuffer toAppendTo,                                     FieldPosition fieldPosition)    {        if (obj instanceof Calendar)            return format( (Calendar)obj, toAppendTo, fieldPosition );        else if (obj instanceof Date)            return format( (Date)obj, toAppendTo, fieldPosition );        else if (obj instanceof Number)            return format( new Date(((Number)obj).longValue()),                          toAppendTo, fieldPosition );        else            throw new IllegalArgumentException("Cannot format given Object (" +                                               obj.getClass().getName() + ") as a Date");    }

    public StringBuffer format(Date date, StringBuffer toAppendTo,                                     FieldPosition fieldPosition) {        // Use our Calendar object        calendar.setTime(date);        return format(calendar, toAppendTo, fieldPosition);    }