java8 时间日期的使用与格式化示例代码详解

// 日期
LocalDate localDate = LocalDate.now();

System.out.println(localDate); // yyyy-MM-dd
System.out.println(localDate.getYear()); // 年
System.out.println(localDate.getMonth()); // 月
System.out.println(localDate.getMonthValue()); // 月
System.out.println(localDate.getDayOfMonth()); // 日
System.out.println(localDate.atStartOfDay()); // 获取今天的开始时间

LocalDate localDate1 = LocalDate.of(2019, 10, 18);
LocalDate localDate2 = LocalDate.of(2019, 10, 17);

System.out.println(localDate1.isBefore(localDate2));

System.out.println(localDate1.plusDays(110));
System.out.println(localDate1.minusMonths(18));

// 时间
LocalTime localTime = LocalTime.now();
System.out.println(localTime); // 09:36:11.619011900
System.out.println(localTime.getHour()); // 时
System.out.println(localTime.getMinute()); // 分
System.out.println(localTime.getSecond()); // 秒
System.out.println(localTime.getNano()); // 纳秒

// 时间 + 日期
LocalDateTime localDateTime = LocalDateTime.of(localDate, localTime);
System.out.println(localDateTime); // 2022-06-27T09:36:11.619011900

Instant instant = Instant.now();
System.out.println(instant.toEpochMilli()); // 时间戳 毫秒 13位
System.out.println(instant.getEpochSecond()); // 时间戳 秒 10位

LocalTime localTime1 = LocalTime.now();
LocalTime localTime2 = localTime1.plusSeconds(100);

Duration duration = Duration.between(localTime1, localTime2);

System.out.println(duration.getSeconds()); // 100

LocalDate localDate1 = LocalDate.of(2019, 10, 18);
LocalDate localDate2 = LocalDate.of(2019, 10, 17);

Period period = Period.between(localDate1, localDate2);

System.out.println(period.getDays()); // -1

// 时间->字符串
LocalDate localDate = LocalDate.now();
System.out.println(localDate); // yyyy-MM-dd
System.out.println(localDate.format(DateTimeFormatter.ISO_DATE));

System.out.println(localDate.format(DateTimeFormatter.ofPattern("yyyy/MM/dd")));

// 字符串->时间
LocalDate date = LocalDate.parse("2019-10-18", DateTimeFormatter.ISO_DATE);
System.out.println(date);

System.out.println(LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));

// Date to Instant
Instant timestamp = new Date().toInstant();

// Date to LocalDateTime
ZoneId zone = ZoneId.systemDefault();
LocalDateTime localDateTime = LocalDateTime.ofInstant(timestamp, zone);
System.out.println(localDateTime);

// Instant to Date
Date date = Date.from(timestamp);
System.out.println(date);