LocalDate、LocalDateTime與timestamp、Date的轉換

1.LocalDate轉Date

LocalDate nowLocalDate = LocalDate.now();
Date date = Date.from(nowLocalDate.atStartOfDay(ZoneId.systemDefault()).toInstant());

2.LocalDateTime轉Date

LocalDateTime localDateTime = LocalDateTime.now();
Date date = Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());

3.Date轉LocalDateTime(LocalDate)

Date date = new Date();
LocalDateTime localDateTime = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
LocalDate localDate = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();

4.LocalDate轉時間戳

LocalDate localDate = LocalDate.now();
long timestamp = localDate.atStartOfDay(ZoneId.systemDefault()).toInstant().toEpochMilli();

5.LocalDateTime轉時間戳

LocalDateTime localDateTime = LocalDateTime.now();
long timestamp = localDateTime.toInstant(ZoneOffset.ofHours(8)).toEpochMilli();

//獲取秒數
Long second = LocalDateTime.now().toEpochSecond(ZoneOffset.of("+8"));
//獲取毫秒數
Long milliSecond = LocalDateTime.now().toInstant(ZoneOffset.of("+8")).toEpochMilli();

6.時間戳轉LocalDateTime(LocalDate)

long timestamp = System.currentTimeMillis();
LocalDate localDate = Instant.ofEpochMilli(timestamp).atZone(ZoneId.systemDefault()).toLocalDate();
LocalDateTime localDateTime = Instant.ofEpochMilli(timestamp).atZone(ZoneId.systemDefault()).toLocalDateTime();

7.LocalDateTime與String互轉

//時間轉字符串格式化
 DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS");
 String dateTime = LocalDateTime.now(ZoneOffset.of("+8")).format(formatter);
 
//字符串轉時間
String dateTimeStr = "2018-07-28 14:11:15";
DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
LocalDateTime dateTime = LocalDateTime.parse(dateTimeStr, df);

8.LocalDate計算相隔天數

   // 開始日期
LocalDate startDate = LocalDate.parse("2020-05-08");
// 結束日期
LocalDate endDate = LocalDate.parse("2020-06-09");
// 剩余天數
int lastDayInt = (int) (endDate.toEpochDay() - startDate.toEpochDay());

另外可以使用DAYS.between(day0, day1)就可以計算出相應的天數。
9.獲取月初與月末

//獲取月初
 LocalDate monthOfFirstDate=LocalDate.parse(count_date,
                DateTimeFormatter.ofPattern("yyyy-MM-dd")).with(TemporalAdjusters.firstDayOfMonth());
//獲取月末
 LocalDate monthOfLastDate=LocalDate.parse(count_date,
                DateTimeFormatter.ofPattern("yyyy-MM-dd")).with(TemporalAdjusters.lastDayOfMonth())