Java 8 新的时间和日期API
Java 8的日期和时间类包含 LocalDate、LocalTime、Instant、Duration 以及 Period ,这些类都包含在 java.time 包中,Java 8 新的时间API的使用方式,包括创建、格式化、解析、计算、修改,下面我们看下如何去使用。 作者:liuren
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来源:GitHub
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// 获取当前年月日
LocalDate localDate = LocalDate.now();
System.out.println(localDate);
// 构造指定的年月日
LocalDate localDate1 = LocalDate.of(2019, 9, 12);
System.out.println(localDate1);
// 获取年、月、日、星期几
int year = localDate.getYear();
int year1 = localDate.get(ChronoField.YEAR);
Month month = localDate.getMonth();
int month1 = localDate.get(ChronoField.MONTH_OF_YEAR);
int day = localDate.getDayOfMonth();
int day1 = localDate.get(ChronoField.DAY_OF_MONTH);
DayOfWeek dayOfWeek = localDate.getDayOfWeek();
int dayOfWeek1 = localDate.get(ChronoField.DAY_OF_WEEK);
log.error("{}=>{}=>{}=>{}=>{}=>{}=>{}=>{}", year,year1,month,month1,day,day1,dayOfWeek,dayOfWeek1);
2020-01-02
2019-09-12
16:59:03.091 [main] ERROR cn.codepeople.util.SpringTest - 2020=>2020=>JANUARY=>1=>2=>2=>THURSDAY=>4
如何使用,使用方法如下:
LocalTime localTime = LocalTime.of(14, 14, 14);
LocalTime localTime1 = LocalTime.now();
// 获取小时
int hour = localTime.getHour();
int hour1 = localTime.get(ChronoField.HOUR_OF_DAY);
// 获取分
int minute = localTime.getMinute();
int minute1 = localTime.get(ChronoField.MINUTE_OF_HOUR);
// 获取秒
int second = localTime.getMinute();
int second1 = localTime.get(ChronoField.SECOND_OF_MINUTE);
log.error("{}=>{}=>{}=>{}=>{}=>{}=>{}=>{}", localTime,localTime1,hour,hour1,minute,minute1,second,second1);
14:14:14=>17:00:52.431=>14=>14=>14=>14=>14=>14
如果类型变化会获取不到指定的值
// 创建 LocalDateTime
LocalDateTime localDateTime = LocalDateTime.now();
LocalDateTime localDateTime1 = LocalDateTime.of(2019, Month.SEPTEMBER, 10, 14, 46, 56);
// 获取LocalDate
LocalDate localDate2 = localDateTime.toLocalDate();
// 获取LocalTime
LocalTime localTime2 = localDateTime.toLocalTime();
log.error("{}=>{}=>{}", localDateTime,localDateTime1,localDate2,localTime2);
2020-01-02T17:03:40.032=>2019-09-10T14:46:56=>2020-01-02
Instant 获取秒数,用于表示一个时间戳(精确到纳秒)
如果只是为了获取秒数或者毫秒数,可以使用 System.currentTimeMillis()。
// 创建Instant对象
Instant instant = Instant.now();
// 获取秒数
long currentSecond = instant.getEpochSecond();
// 获取毫秒数
long currentMilli = instant.toEpochMilli();
Duration 表示一个时间段
// Duration.between()方法创建 Duration 对象
LocalDateTime from = LocalDateTime.of(2017, Month.JANUARY, 1, 00, 0, 0); // 2017-01-01 00:00:00
LocalDateTime to = LocalDateTime.of(2019, Month.SEPTEMBER, 12, 14, 28, 0); // 2019-09-15 14:28:00
Duration duration = Duration.between(from, to); // 表示从 from 到 to 这段时间
long days = duration.toDays(); // 这段时间的总天数
long hours = duration.toHours(); // 这段时间的小时数
long minutes = duration.toMinutes(); // 这段时间的分钟数
long seconds = duration.getSeconds(); // 这段时间的秒数
long milliSeconds = duration.toMillis(); // 这段时间的毫秒数
long nanoSeconds = duration.toNanos(); // 这段时间的纳秒数
LocalDate、LocalTime、LocalDateTime、Instant 为不可变对象,修改这些对象对象会返回一个副本。
增加、减少年数、月数、天数等,以LocalDateTime为例:
LocalDateTime localDateTime = LocalDateTime.of(2019, Month.SEPTEMBER, 12, 14, 32, 0);
// 增加一年
localDateTime = localDateTime.plusYears(1);
localDateTime = localDateTime.plus(1, ChronoUnit.YEARS);
// 减少一个月
localDateTime = localDateTime.minusMonths(1);
localDateTime = localDateTime.minus(1, ChronoUnit.MONTHS);
// 通过with修改某些值
// 修改年为2020
localDateTime = localDateTime.withYear(2020);
localDateTime = localDateTime.with(ChronoField.YEAR, 2020);
// 时间计算
// 获取该年的第一天
LocalDate localDate = LocalDate.now();
LocalDate localDate1 = localDate.with(firstDayOfYear());
时间格式化
LocalDateTime localDate1 = LocalDateTime.now();
LocalDateTime localDate2 = LocalDateTime.now();
// 自定义格式化
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
String s3 = localDate1.format(dateTimeFormatter);
String s4 = localDate2.format(dateTimeFormatter);
log.error("{}",s3);
log.error("{}",s4);
17:13:21.684 [main] ERROR cn.codepeople.util.SpringTest - 2020-01-02 17:13:21
17:13:21.690 [main] ERROR cn.codepeople.util.SpringTest - 2020-01-02 17:13:21
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