//localdatetime -> string
        LocalDateTime now = LocalDateTime.now();
        String format = now.format(DateTimeFormatter.ofPattern("yyyy-MM-dd hh:mm:ss"));
        System.out.println(format);
        
        
        
        //date和localdatetime转换依靠instant中间
        LocalDateTime.ofInstant(new Date().toInstant(), ZoneId.systemDefault());//date -> localdatetime
        Date.from(LocalDateTime.now().atZone(ZoneId.systemDefault()).toInstant());//localdatetime -> date
        

        LocalDate parse = LocalDate.parse("2017-01-05");
        System.out.println(parse);
        
        LocalTime parse2 = LocalTime.parse("12:12:12");
        System.out.println(parse2);
        //datetimeformatter有严格的大小写区分HH是24小时制度hh是12小时制度
        LocalDateTime parse3 = LocalDateTime.parse("2017-01-0512:12:12",DateTimeFormatter.ofPattern("yyyy-MM-ddHH:mm:ss"));
        System.out.println(parse3);
        
        LocalDateTime.parse("2017-01-05T12:12:12");//默认解析date和time之间必须有字符T
        
        
        //simpledateformat没有严格的大小写区分
        Date parse4 = new SimpleDateFormat("yyyy-mm-dd HH:mm:ss").parse("2012-01-05 06:12:12");
        System.out.println(parse4);