java8新特性LocalDate、LocalTime、LocalDateTime的學習
阿新 • • 發佈：2020-11-24
以前操作時間都是使用SimpleDateFormat類改變Date的時間格式，使用Calendar類操作時間。但是SimpleDateFormat是執行緒不安全的，原始碼如下：
1 private StringBuffer format(Date date, StringBuffer toAppendTo,
2 FieldDelegate delegate) {
3 // Convert input date to time field list
4 calendar.setTime(date);
5
6 boolean useDateFormatSymbols = useDateFormatSymbols();
7
8 for (int i = 0; i < compiledPattern.length; ) {
9 int tag = compiledPattern[i] >>> 8;
10 int count = compiledPattern[i++] & 0xff;
11 if (count == 255) {
12 count = compiledPattern[i++] << 16;
13 count |= compiledPattern[i++];
14 }
15
16 switch (tag) {
17 case TAG_QUOTE_ASCII_CHAR:
18 toAppendTo.append((char)count);
19 break;
20
21 case TAG_QUOTE_CHARS:
22 toAppendTo.append(compiledPattern, i, count);
23 i += count;
24 break;
25
26 default:
27 subFormat(tag, count, delegate, toAppendTo, useDateFormatSymbols);
28 break;
29 }
30 }
31 return toAppendTo;
32 }
calendar是共享變數，並且這個共享變數沒有做執行緒安全控制。當多個執行緒同時使用相同的SimpleDateFormat物件呼叫format方法時，多個執行緒會同時呼叫calendar.setTime方法，可能一個執行緒剛設定好time值另外的一個執行緒馬上把設定的time值給修改了導致返回的格式化時間可能是錯誤的。
所以JAVA8推出了LocalDate、LocalTime、LocalDateTime是執行緒安全、簡易、高可靠的時間包。原始碼如下
-
LocalDate 獲取年月日
1 @Test 2 public void localDataTest(){ 3 //建立LocalDate獲取當前年月日 4 LocalDate now = LocalDate.now(); 5 System.out.println("當前時間：" + now); 6 //構造指定的年月日 7 LocalDate localDate = LocalDate.of(2020, 11, 24); 8 System.out.println("當前指定時間：" + localDate); 9 int year = now.getYear(); 10 System.out.println("當前年year：" + year); 11 int year1 = now.get(ChronoField.YEAR); 12 System.out.println("當前年year1：" + year1); 13 Month month = now.getMonth(); 14 System.out.println("當前月month：" + month); 15 int month1 = now.get(ChronoField.MONTH_OF_YEAR); 16 System.out.println("當前月month1：" + month1); 17 int day = now.getDayOfMonth(); 18 System.out.println("當前天day：" + day); 19 int day1 = now.get(ChronoField.DAY_OF_MONTH); 20 System.out.println("當前天day1：" + day1); 21 DayOfWeek dayOfWeek = now.getDayOfWeek(); 22 System.out.println("當前星期幾dayOfWeek：" + dayOfWeek); 23 int dayOfWeek1 = now.get(ChronoField.DAY_OF_WEEK); 24 System.out.println("當前星期幾dayOfWeek1：" + dayOfWeek1); 25 } -
LocalTime 獲取時分秒
1 @Test 2 public void localTimeTest(){ 3 //建立LocalTime獲取當前時分秒 4 LocalTime now = LocalTime.now(); 5 System.out.println("當前時間：" + now); 6 LocalTime localTime = LocalTime.of(13, 51, 10); 7 System.out.println("指定時間：" + localTime); 8 int hour = now.getHour(); 9 System.out.println("當前小時數hour："+ hour); 10 int hour1 = now.get(ChronoField.HOUR_OF_DAY); 11 System.out.println("當前小時數hour1："+ hour1); 12 int minute = now.getMinute(); 13 System.out.println("當前分鐘數minute："+ minute); 14 int minute1 = now.get(ChronoField.MINUTE_OF_DAY); 15 System.out.println("當前分鐘數minute1："+ minute1); 16 int second = now.getSecond(); 17 System.out.println("當前秒數second："+ second); 18 int second1 = now.get(ChronoField.SECOND_OF_MINUTE); 19 System.out.println("當前秒數second1："+ second1); 20 } -
LocalDateTime 獲取年月日時分秒，相當於LocalDate+LocalTime，可與LocalDate、LocalTime相互轉換
1 @Test 2 public void localDataTimeTest(){ 3 //建立localDateTime獲取當前年月日時分秒 4 LocalDateTime localDateTime = LocalDateTime.now(); 5 System.out.println("當前時間：" + localDateTime); 6 LocalDateTime localDateTime1 = LocalDateTime.of(2020, Month.SEPTEMBER, 10, 14, 46, 56); 7 System.out.println("指定時間：" + localDateTime1); 8 LocalDateTime of = LocalDateTime.of(LocalDate.now(), LocalTime.now()); 9 System.out.println("當前時間1：" + of); 10 LocalDateTime localDateTime2 = LocalDate.now().atTime(LocalTime.now()); 11 System.out.println("當前時間2：" + localDateTime2); 12 LocalDateTime localDateTime3 = LocalTime.now().atDate(LocalDate.now()); 13 System.out.println("當前時間3：" + localDateTime3); 14 LocalDate localDate = localDateTime.toLocalDate(); 15 System.out.println("當前年月日：" + localDate); 16 LocalTime localTime = localDateTime.toLocalTime(); 17 System.out.println("當前時分秒：" + localTime); 18 } -
Period 時間長度類 Period表示以年、月、日衡量的時長，通過Period增加、減少年月日
1 @Test 2 public void periodTest(){ 3 //建立localDateTime獲取當前年月日時分秒 4 LocalDateTime localDateTime = LocalDateTime.now(); 5 //建立Period物件，設定一年 6 Period period = Period.ofYears(1); 7 //增加一年 8 LocalDate localDate = localDateTime.toLocalDate().plus(period); 9 System.out.println("增加一年後的時間：" + localDate); 10 Period period1 = Period.ofYears(-1); 11 //減少一年 12 LocalDate localDate1 = localDateTime.toLocalDate().plus(period1); 13 System.out.println("減少一年後的時間：" + localDate1); 14 //建立Period物件，設定一月 15 Period period2 = Period.ofMonths(1); 16 //增加一個月 17 LocalDate localDate2 = localDateTime.toLocalDate().plus(period2); 18 System.out.println("增加一個月後的時間：" + localDate2); 19 //建立Period物件，設定一週 20 Period period3 = Period.ofWeeks(1); 21 //增加一週 22 LocalDate localDate3 = localDateTime.toLocalDate().plus(period3); 23 System.out.println("增加一週後的時間：" + localDate3); 24 //建立Period物件，設定一天 25 Period period4 = Period.ofDays(1); 26 //增加一天 27 LocalDate localDate4 = localDateTime.toLocalDate().plus(period4); 28 System.out.println("增加一天後的時間：" + localDate4); 29 } -
Duration 時間長度類 Duration表示以時、分、秒衡量的時長，通過Duration增加、減少時分秒
1 @Test 2 public void durationTest(){ 3 //建立localDateTime獲取當前時間時分秒 4 LocalDateTime localDateTime = LocalDateTime.now(); 5 //建立Duration物件，設定1天 6 Duration duration = Duration.ofDays(1); 7 //增加一天 8 LocalTime localTime = localDateTime.toLocalTime().plus(duration); 9 System.out.println("增加一天後時間：" + localTime); 10 //建立Duration物件，設定一小時 11 Duration duration1 = Duration.ofHours(-1); 12 //減少一天 13 LocalTime localTime1 = localDateTime.toLocalTime().plus(duration1); 14 System.out.println("增加一天後時間：" + localTime1); 15 //建立Duration物件，設定一小時 16 Duration duration2 = Duration.ofHours(1); 17 //增加一小時 18 LocalTime localTime2 = localDateTime.toLocalTime().plus(duration2); 19 System.out.println("增加一小時後時間：" + localTime2); 20 //建立Duration物件，設定一分鐘 21 Duration duration3 = Duration.ofMinutes(1); 22 //增加一分鐘 23 LocalTime localTime3 = localDateTime.toLocalTime().plus(duration3); 24 System.out.println("增加一分鐘後時間：" + localTime3); 25 //建立Duration物件，設定十秒鐘 26 Duration duration4 = Duration.ofSeconds(10); 27 //增加十秒鐘 28 LocalTime localTime4 = localDateTime.toLocalTime().plus(duration4); 29 System.out.println("增加十秒鐘後時間：" + localTime4); 30 //建立Duration物件，設定一百毫秒 31 Duration duration5 = Duration.ofMillis(100); 32 //增加一百毫秒 33 LocalTime localTime5 = localDateTime.toLocalTime().plus(duration5); 34 System.out.println("增加一百毫秒後時間：" + localTime5); 35 } -
ZonedDateTime 時區處理類 可以設定時區，用法和LocalDataTime基本相同
@Test public void zonedDateTimeTest(){ ZoneId zoneId = ZoneId.of("UTC+1"); //設定指定時間、時區 ZonedDateTime zonedDateTime = ZonedDateTime.of(2020, 11, 24, 15, 29, 53, 1026, zoneId); //獲取今天是今年第幾天 int dayOfYear = zonedDateTime.getDayOfYear(); System.out.println("今天是今年第"+dayOfYear+"天"); //獲取今天是這月第幾天 int dayOfMonth = zonedDateTime.getDayOfMonth(); System.out.println("今天是這月第"+dayOfMonth+"天"); //獲取今天是這周第幾天 int dayOfWeek = zonedDateTime.getDayOfWeek().get(ChronoField.DAY_OF_WEEK); System.out.println("今天是這周第"+dayOfWeek+"天"); //增加一年 ZonedDateTime zonedDateTime1 = zonedDateTime.plusYears(1); System.out.println("增加一年後的時間："+zonedDateTime1); //減少一年 ZonedDateTime zonedDateTime2 = zonedDateTime.minusYears(1); System.out.println("減少一年後的時間："+zonedDateTime2); }