//獲取當前時間
        System.out.println(LocalDateTime.now());
        //獲取當前時間時分秒
        System.out.println(LocalDateTime.now().toLocalTime());
        //獲取當前時間年月日
        System.out.println(LocalDateTime.now().toLocalDate());
        //獲取當前時間20天之前
        System.out.println(LocalDateTime.now().minusDays(20
 
));
        //獲取當前時間20天之後
        System.out.println(LocalDateTime.now().plusDays(20));
        //獲取當前時間60天之前
        System.out.println(LocalDateTime.now().minusDays(60));
        //所有minus開頭都是之前    plus開頭都是之後
        
        //比較大小
        System.out.println(LocalDateTime.now().compareTo(LocalDateTime.now().plusDays(2
 
)));

        //例項化方式   以及比較大小
        Duration between = Duration.between(LocalDateTime.of(1993,3,14,0,0), LocalDateTime.now());
        Duration between2 = Duration.between(LocalDateTime.of(1993,3,14,0,0), LocalDateTime.now());
        System.out.println(between.toDays());
        System.out.println(between2.toDays());

1.獲取當前年月日的字串

String ymd = LocalDate.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));