Java获取当月第一天

Java获取当月第一天

public static String getFirstDay() {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Calendar calendar = Calendar.getInstance();
        Date theDate = calendar.getTime();
        GregorianCalendar gcLast = (GregorianCalendar) Calendar.getInstance();
        gcLast.setTime(theDate);
        gcLast.set(Calendar.DAY_OF_MONTH, 1);
        String day_first = df.format(gcLast.getTime());
        //StringBuffer str = new StringBuffer().append(day_first).append(" 00:00:00");
        StringBuffer str = new StringBuffer().append(day_first);
        return str.toString();
    }