SimpleDateFormatでJava String/Date型の変換

public class TestSimpleDateFormat {
    //パターン定義
    private static final String DATE_PATTERN = "yyyy.MM.dd HH:mm";

    //Date日付型をString文字列型へ変換
    private static String _date2string(Date date) {
        SimpleDateFormat sdf = new SimpleDateFormat(DATE_PATTERN);
        return sdf.format(date);
    }
    
    //String文字列型をDate日付型へ変換
    private static Date _string2date(String value) {
        SimpleDateFormat sdf = new SimpleDateFormat(DATE_PATTERN);
        try {
            return sdf.parse(value);
        } catch (ParseException e) {
            return null;
        }
    }
    
    //テスト
    public static void main(String []args) {
        //Date日付型をString文字列型へ変換
        Date date1 = Calendar.getInstance().getTime();
        String strDate1 = _date2string(date);
        System.out.println(strDate1);
        
        //String文字列型をDate日付型へ変換
        Date date2 = _string2date("2009.01.01 23:55")
        System.out.println(date2);
    }
}