線程安全的LocalDateTime的各種轉換

1.將LocalDateTime轉為自定義的時間格式的字符串

public static String getDateTimeAsString(LocalDateTime localDateTime, String format) {

　　DateTimeFormatter formatter = DateTimeFormatter.ofPattern(format);

　　return localDateTime.format(formatter);

}

 

 

2.將long類型的timestamp轉為LocalDateTime

public static LocalDateTime getDateTimeOfTimestamp(long timestamp) {

　　 Instant instant = Instant.ofEpochMilli(timestamp);

　　ZoneId zone = ZoneId.systemDefault();

　　return LocalDateTime.ofInstant(instant, zone);

}

 

3.將LocalDateTime轉為long類型的timestamp

　　public static long getTimestampOfDateTime(LocalDateTime localDateTime) {

　　ZoneId zone = ZoneId.systemDefault();

　　Instant instant = localDateTime.atZone(zone).toInstant();

　　return instant.toEpochMilli();

}

 

4.將某時間字符串轉為自定義時間格式的LocalDateTime

public static LocalDateTime parseStringToDateTime(String time, String format) {

　　DateTimeFormatter df = DateTimeFormatter.ofPattern(format);

　　return LocalDateTime.parse(time, df);

}

 

5.附一個獲取當日凌晨時間戳的方式

@Test
public void testSystem(){
   Calendar c = Calendar.getInstance();
   c.set(Calendar.HOUR_OF_DAY, 0);
   c.set(Calendar.MINUTE, 0);
   c.set(Calendar.SECOND, 0);
   c.set(Calendar.MILLISECOND, 0);
   long timeInMillis = c.getTimeInMillis();
   Instant instant = Instant.ofEpochMilli(timeInMillis);
   ZoneId zone = ZoneId.systemDefault();
   LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone);
   DateTimeFormatter format = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
   String format = format.format( localDateTime);
   System.out.println(format);
}

最后看懂這個代碼， 就提升了
long now = System.currentTimeMillis() / 1000l;

long daySecond = 60 * 60 * 24;

long dayTime = now - (now + 8 * 3600) % daySecond;

long nowTime =System.currentTimeMillis();
long todayStartTime =nowTime - ((nowTime + TimeZone.getDefault().getRawOffset()) % (24 * 60 * 60 * 1000L));