public static String getFirstDayOfMonth() {
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.DATE, 1);
        return format(DF_DATE, cal.getTime());
    }
public static String getFirstDayOfMonth() {
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.DATE, 1);
        return format(DF_DATE, cal.getTime());
    }
public static String getFirstDayOfMonth ( ) { Calendar cal = Calendar . getInstance ( ) ; cal . set ( Calendar . DATE , 1 ) ; return format ( DF_DATE , cal . getTime ( ) ) ; }
获取本月第一天

@return 本月第一天
获取本月第一天