基础用法

LocalDateTime now = LocalDateTime.now()

LocalDateTime转Date

LocalDateTime now = LocalDateTime.now();
ZonedDateTime zonedDateTime1 = now.atZone(ZoneId.systemDefault());
//或者 ZonedDateTime zonedDateTime = now.atZone(ZoneId.of("+8"));
//注意：Instant是桥梁
Date date = Date.from(zonedDateTime.toInstant());

Date转LocalDateTime

 Date date = new Date();
 Instant instant = date.toInstant();
 LocalDateTime now = LocalDateTime.ofInstant(instant, ZoneId.systemDefault());

时区

时区用Zone表示，UTC是协调世界时间，中国的时区是正八区（即UTC+8)
所以可以使用ZoneId.of(“+8”)表示中国，或者使用ZoneId.of(“Asia/Shanghai”)

格式化

//格式化当前日期
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd");
String now_date = LocalDateTime.now().format(formatter);
System.out.println(now_date);//20200316

时间间隔

LocalDateTime now = LocalDateTime.now();
LocalDateTime updateTime = node.getUpdateTime();
long duration = Duration.between(now, updateTime).toMillis();

年月日间隔

LocalDate today = LocalDate.now();
for (String uploadKey : uploadKeys) {
    //181 21 12 13 0001
    //格式说明:
    //1-3: 机位
    //4-9: 年月日
    //10以后: 自增id
    String taskKey = uploadKey.replace(RedisUtil.SRS_UPLOAD_SLICE_PREFIX, "");
    LocalDate date = LocalDate.parse(taskKey.substring(3, 9), formatter);
    long duration = ChronoUnit.DAYS.between(date, today);
    if (duration > 2) {
        deleteKeys.add(uploadKey);
    }
}

比较大小

@Test
    public void localDateTimeCompare() {
        LocalDateTime now = LocalDateTime.now();
        LocalDateTime future = now.plusSeconds(20);
        int i = now.compareTo(future);
        System.out.println(i);
    }