• java8新特性LocalDate、LocalTime、LocalDateTime的学习

    以前操作时间都是使用SimpleDateFormat类改变Date的时间格式，使用Calendar类操作时间。但是SimpleDateFormat是线程不安全的，源码如下：

     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是共享变量，并且这个共享变量没有做线程安全控制。当多个线程同时使用相同的SimpleDateFormat对象调用format方法时，多个线程会同时调用calendar.setTime方法，可能一个线程刚设置好time值另外的一个线程马上把设置的time值给修改了导致返回的格式化时间可能是错误的。

    所以JAVA8推出了LocalDate、LocalTime、LocalDateTime是线程安全、简易、高可靠的时间包。源码如下

    1. LocalDate  获取年月日

       1 @Test
 2 public void localDataTest(){
 3     //创建LocalDate获取当前年月日
 4     LocalDate now = LocalDate.now();
 5     System.out.println("当前时间：" + now);
 6     //构造指定的年月日
 7     LocalDate localDate = LocalDate.of(2020, 11, 24);
 8     System.out.println("当前指定时间：" + localDate);
 9     int year = now.getYear();
10     System.out.println("当前年year：" + year);
11     int year1 = now.get(ChronoField.YEAR);
12     System.out.println("当前年year1：" + year1);
13     Month month = now.getMonth();
14     System.out.println("当前月month：" + month);
15     int month1 = now.get(ChronoField.MONTH_OF_YEAR);
16     System.out.println("当前月month1：" + month1);
17     int day = now.getDayOfMonth();
18     System.out.println("当前天day：" + day);
19     int day1 = now.get(ChronoField.DAY_OF_MONTH);
20     System.out.println("当前天day1：" + day1);
21     DayOfWeek dayOfWeek = now.getDayOfWeek();
22     System.out.println("当前星期几dayOfWeek：" + dayOfWeek);
23     int dayOfWeek1 = now.get(ChronoField.DAY_OF_WEEK);
24     System.out.println("当前星期几dayOfWeek1：" + dayOfWeek1);
25  }

    2. LocalTime   获取时分秒

       1 @Test
 2 public void localTimeTest(){
 3     //创建LocalTime获取当前时分秒
 4     LocalTime now = LocalTime.now();
 5     System.out.println("当前时间：" + now);
 6     LocalTime localTime = LocalTime.of(13, 51, 10);
 7     System.out.println("指定时间：" + localTime);
 8     int hour = now.getHour();
 9     System.out.println("当前小时数hour："+ hour);
10     int hour1 = now.get(ChronoField.HOUR_OF_DAY);
11     System.out.println("当前小时数hour1："+ hour1);
12     int minute = now.getMinute();
13     System.out.println("当前分钟数minute："+ minute);
14     int minute1 = now.get(ChronoField.MINUTE_OF_DAY);
15     System.out.println("当前分钟数minute1："+ minute1);
16     int second = now.getSecond();
17     System.out.println("当前秒数second："+ second);
18     int second1 = now.get(ChronoField.SECOND_OF_MINUTE);
19     System.out.println("当前秒数second1："+ second1);
20 }

    3. LocalDateTime   获取年月日时分秒，相当于LocalDate+LocalTime，可与LocalDate、LocalTime相互转换

       1 @Test
 2 public void localDataTimeTest(){
 3     //创建localDateTime获取当前时间时分秒
 4     LocalDateTime localDateTime = LocalDateTime.now();
 5     System.out.println("当前时间：" + localDateTime);
 6     LocalDateTime localDateTime1 = LocalDateTime.of(2020, Month.SEPTEMBER, 10, 14, 46, 56);
 7     System.out.println("指定时间：" + localDateTime1);
 8     LocalDateTime of = LocalDateTime.of(LocalDate.now(), LocalTime.now());
 9     System.out.println("当前时间1：" + of);
10     LocalDateTime localDateTime2 = LocalDate.now().atTime(LocalTime.now());
11     System.out.println("当前时间2：" + localDateTime2);
12     LocalDateTime localDateTime3 = LocalTime.now().atDate(LocalDate.now());
13     System.out.println("当前时间3：" + localDateTime3);
14     LocalDate localDate = localDateTime.toLocalDate();
15     System.out.println("当前年月日：" + localDate);
16     LocalTime localTime = localDateTime.toLocalTime();
17     System.out.println("当前时分秒：" + localTime);
18     //时间格式转换成yyyy-MM-dd HH:mm:ss
19     String timeStr1=LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
20     String timeStr2=LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS"));
21     System.out.println("当前时间为:"+timeStr1);
22     System.out.println("当前时间为:"+timeStr2);
23 }

    4. Period  时间长度类   Period表示以年、月、日衡量的时长，通过Period增加、减少年月日

       1 @Test
 2 public void periodTest(){
 3     //创建localDateTime获取当前年月日时分秒
 4     LocalDateTime localDateTime = LocalDateTime.now();
 5     //创建Period对象，设置一年
 6     Period period = Period.ofYears(1);
 7     //增加一年
 8     LocalDate localDate = localDateTime.toLocalDate().plus(period);
 9     System.out.println("增加一年后的时间：" + localDate);
10     Period period1 = Period.ofYears(-1);
11     //减少一年
12     LocalDate localDate1 = localDateTime.toLocalDate().plus(period1);
13     System.out.println("减少一年后的时间：" + localDate1);
14     //创建Period对象，设置一月
15     Period period2 = Period.ofMonths(1);
16     //增加一个月
17     LocalDate localDate2 = localDateTime.toLocalDate().plus(period2);
18     System.out.println("增加一个月后的时间：" + localDate2);
19     //创建Period对象，设置一周
20     Period period3 = Period.ofWeeks(1);
21     //增加一周
22     LocalDate localDate3 = localDateTime.toLocalDate().plus(period3);
23     System.out.println("增加一周后的时间：" + localDate3);
24     //创建Period对象，设置一天
25     Period period4 = Period.ofDays(1);
26     //增加一天
27     LocalDate localDate4 = localDateTime.toLocalDate().plus(period4);
28     System.out.println("增加一天后的时间：" + localDate4);
29 }

    5. Duration  时间长度类   Duration表示以时、分、秒衡量的时长，通过Duration增加、减少时分秒

       1 @Test
 2 public void durationTest(){
 3       //创建localDateTime获取当前时间时分秒
 4       LocalDateTime localDateTime = LocalDateTime.now();
 5       //创建Duration对象，设置1天
 6       Duration duration = Duration.ofDays(1);
 7       //增加一天
 8       LocalTime localTime = localDateTime.toLocalTime().plus(duration);
 9       System.out.println("增加一天后时间：" + localTime);
10       //创建Duration对象，设置一小时
11       Duration duration1 = Duration.ofHours(-1);
12       //减少一天
13       LocalTime localTime1 = localDateTime.toLocalTime().plus(duration1);
14       System.out.println("增加一天后时间：" + localTime1);
15       //创建Duration对象，设置一小时
16       Duration duration2 = Duration.ofHours(1);
17       //增加一小时
18       LocalTime localTime2 = localDateTime.toLocalTime().plus(duration2);
19       System.out.println("增加一小时后时间：" + localTime2);
20       //创建Duration对象，设置一分钟
21       Duration duration3 = Duration.ofMinutes(1);
22       //增加一分钟
23       LocalTime localTime3 = localDateTime.toLocalTime().plus(duration3);
24       System.out.println("增加一分钟后时间：" + localTime3);
25       //创建Duration对象，设置十秒钟
26       Duration duration4 = Duration.ofSeconds(10);
27       //增加十秒钟
28       LocalTime localTime4 = localDateTime.toLocalTime().plus(duration4);
29       System.out.println("增加十秒钟后时间：" + localTime4);
30       //创建Duration对象，设置一百毫秒
31       Duration duration5 = Duration.ofMillis(100);
32       //增加一百毫秒
33       LocalTime localTime5 = localDateTime.toLocalTime().plus(duration5);
34       System.out.println("增加一百毫秒后时间：" + localTime5);
35 }

    6. ZonedDateTime   时区处理类   可以设置时区，用法和LocalDataTime基本相同

      @Test
public void zonedDateTimeTest(){
    ZoneId zoneId = ZoneId.of("UTC+1");
    //设置指定时间、时区
    ZonedDateTime zonedDateTime = ZonedDateTime.of(2020, 11, 24, 15, 29, 53, 1026, zoneId);
    //获取今天是今年第几天
    int dayOfYear = zonedDateTime.getDayOfYear();
    System.out.println("今天是今年第"+dayOfYear+"天");
    //获取今天是这月第几天
    int dayOfMonth = zonedDateTime.getDayOfMonth();
    System.out.println("今天是这月第"+dayOfMonth+"天");
    //获取今天是这周第几天
    int dayOfWeek = zonedDateTime.getDayOfWeek().get(ChronoField.DAY_OF_WEEK);
    System.out.println("今天是这周第"+dayOfWeek+"天");
    //增加一年
    ZonedDateTime zonedDateTime1 = zonedDateTime.plusYears(1);
    System.out.println("增加一年后的时间："+zonedDateTime1);
    //减少一年
    ZonedDateTime zonedDateTime2 = zonedDateTime.minusYears(1);
    System.out.println("减少一年后的时间："+zonedDateTime2);
}

      　　
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  • 原文地址：https://www.cnblogs.com/dinghaoran/p/14030652.html
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