Java时间处理方法

1. 当前时间的时间戳

// 获取毫秒数
Long milliSecond = LocalDateTime.now().toInstant(ZoneOfset.of("+8")).toEpochMilli();
// 当前毫秒
Long milliSecond = System.currentTimeMillis();
// 获取当前秒数
Long second = LocalDateTime.now().toEpochSecond(ZoneOffset.of("+8"));

2.LocalDateTime 和 String互转

DateTimeFormatter fmt = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
DateTimeFormatter fmt1 = DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS");
DateTimeFormatter fmt2 = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");
// 字符串转时间
String dateTimeStr = "2021-02-28 14:11:15";
LocalDateTime dateTime = LocalDateTime.parse(dateTimeStr, fmt);
//时间转字符串格式化
Long timeStamp = 1614773350L;
Instant instant = Instant.ofEpochSecond(timestamp);
LocalDateTime ldt = LocalDateTime.ofInstant(timestamp, ZoneId.systemDefault());
String dateTimeStr = ldt.format(fmt1);

3. 时间戳转LocalDateTime

// 时间戳转LocalDateTime
Long timeStamp = 1614773350L;
Instant instant = Instant.ofEpochSecond(timeStamp);
LocalDateTime dateTime = LocalDateTime.ofInstant(instant,ZoneId.systemDefault());

4. 时间戳 转 ISO8601时间格式

//时间转字符串格式化
Long timeStamp = 1614773350L;
try {
    LocalDateTime dt1 = LocalDateTime.ofEpochSecond(timestamp,0, ZoneOffset.ofHours(8));;
    ZoneOffset offset = ZoneOffset.of("+8");
    OffsetDateTime date = OffsetDateTime.of(dt1,offset);
    DateTimeFormatter formatter2=DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");
    String unixTime=date.format(formatter2); 
} catch (DateTimeParseException ex) {
    ex.printStackTrace();
}