Java 8 新特性之日期时间 API 全面解析 (全网最清晰教程)

// 获取当前日期
LocalDate today = LocalDate.now();
System.out.println("Today's date: " + today);

// 获取当前时间
LocalTime now = LocalTime.now();
System.out.println("Current time: " + now);

// 获取当前日期和时间
LocalDateTime nowDateTime = LocalDateTime.now();
System.out.println("Current date and time: " + nowDateTime);

// 创建指定日期
LocalDate specificDate = LocalDate.of(2024, 1, 1);
System.out.println("Specific date: " + specificDate);

// 创建指定时间
LocalTime specificTime = LocalTime.of(14, 30, 0);
System.out.println("Specific time: " + specificTime);

// 创建指定日期和时间
LocalDateTime specificDateTime = LocalDateTime.of(2024, 1, 1, 14, 30, 0);
System.out.println("Specific date and time: " + specificDateTime);

// 使用预定义格式
DateTimeFormatter dateFormatter = DateTimeFormatter.ISO_DATE;
System.out.println("Formatted date (ISO_DATE): " + today.format(dateFormatter));

// 使用自定义格式
DateTimeFormatter customFormatter = DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss");
System.out.println("Formatted date and time (custom): " + nowDateTime.format(customFormatter));

LocalDate tomorrow = today.plusDays(1);
System.out.println("Tomorrow: " + tomorrow);

LocalDate lastWeek = today.minusWeeks(1);
System.out.println("Last week: " + lastWeek);

LocalTime later = now.plusHours(2);
System.out.println("2 hours later: " + later);

LocalDateTime nextMonth = nowDateTime.plusMonths(1);
System.out.println("Next month: " + nextMonth);

// 计算两个日期之间的天数
LocalDate date1 = LocalDate.of(2023, 1, 1);
LocalDate date2 = LocalDate.of(2023, 10, 27);
Period period = Period.between(date1, date2);
System.out.println("Days between date1 and date2: " + period.getDays());

// 计算两个时间之间的小时数
LocalTime time1 = LocalTime.of(10, 0, 0);
LocalTime time2 = LocalTime.of(12, 30, 0);
Duration duration = Duration.between(time1, time2);
System.out.println("Hours between time1 and time2: " + duration.toHours());

// 获取当前时区的日期和时间
ZonedDateTime zonedDateTime = ZonedDateTime.now();
System.out.println("Current date and time with time zone: " + zonedDateTime);

// 指定时区
ZoneId zoneId = ZoneId.of("America/Los_Angeles");
ZonedDateTime losAngelesTime = ZonedDateTime.now(zoneId);
System.out.println("Current date and time in Los Angeles: " + losAngelesTime);

// 获取当前日期和时间与 UTC 的偏移量
OffsetDateTime offsetDateTime = OffsetDateTime.now();
System.out.println("Current date and time with offset: " + offsetDateTime);

// Date 转换为 LocalDate
Date date = new Date();
LocalDate localDate = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
System.out.println("Date to LocalDate: " + localDate);

// LocalDate 转换为 Date
LocalDate localDate2 = LocalDate.now();
Date date2 = Date.from(localDate2.atStartOfDay(ZoneId.systemDefault()).toInstant());
System.out.println("LocalDate to Date: " + date2);

// Calendar 转换为 ZonedDateTime
Calendar calendar = Calendar.getInstance();
ZonedDateTime zonedDateTime2 = ZonedDateTime.ofInstant(calendar.toInstant(), calendar.getTimeZone().toZoneId());
System.out.println("Calendar to ZonedDateTime: " + zonedDateTime2);

// ZonedDateTime 转换为 Calendar
ZonedDateTime zonedDateTime3 = ZonedDateTime.now();
Calendar calendar2 = GregorianCalendar.from(zonedDateTime3);
System.out.println("ZonedDateTime to Calendar: " + calendar2);

LocalDate myDate = LocalDate.now();
myDate.plusDays(1); // 错误：myDate 没有被修改
System.out.println(myDate); // 仍然是今天的日期

LocalDate myDateCorrect = LocalDate.now();
myDateCorrect = myDateCorrect.plusDays(1); // 正确：将结果赋值给 myDateCorrect
System.out.println(myDateCorrect); // 明天的日期