Date、LocalDate、LocalDateTime之间的转换和计算

最新推荐文章于 2025-03-09 12:03:24 发布

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最新推荐文章于 2025-03-09 12:03:24 发布

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分类专栏： java工具文章标签： Date LocalDate LocalDateTime ZoneId Instant

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本文详细介绍如何在Java中进行不同日期时间类之间的转换，包括从java.util.Date到java.time包下LocalDateTime、LocalDate和LocalTime的转换方法，以及相反方向的转换。同时，提供了计算两个LocalDate或LocalDateTime之间相差天数的实用代码。

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// 01. java.util.Date --> java.time.LocalDateTime
public void date2LocalDateTime() {
    Date date = new Date();
    Instant instant = date.toInstant();
    ZoneId zone = ZoneId.systemDefault();
    LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone);
}

// 02. java.util.Date --> java.time.LocalDate
public void date2LocalDate() {
    Date date = new Date();
    Instant instant = date.toInstant();
    ZoneId zone = ZoneId.systemDefault();
    LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone);
    LocalDate localDate = localDateTime.toLocalDate();
}

// 03. java.util.Date --> java.time.LocalTime
public void date2LocalTime() {
    Date date = new Date();
    Instant instant = date.toInstant();
    ZoneId zone = ZoneId.systemDefault();
    LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone);
    LocalTime localTime = localDateTime.toLocalTime();
}


// 04. java.time.LocalDateTime --> java.util.Date
public void localDateTime2Date() {
    LocalDateTime localDateTime = LocalDateTime.now();
    ZoneId zone = ZoneId.systemDefault();
    Instant instant = localDateTime.atZone(zone).toInstant();
    Date date = Date.from(instant);
}


// 05. java.time.LocalDate --> java.util.Date
public void localDate2Date() {
    LocalDate localDate = LocalDate.now();
    ZoneId zone = ZoneId.systemDefault();
    Instant instant = localDate.atStartOfDay().atZone(zone).toInstant();
    Date date = Date.from(instant);
}

// 06. java.time.LocalTime --> java.util.Date
public void localTime2Date() {
    LocalTime localTime = LocalTime.now();
    LocalDate localDate = LocalDate.now();
    LocalDateTime localDateTime = LocalDateTime.of(localDate, localTime);
    ZoneId zone = ZoneId.systemDefault();
    Instant instant = localDateTime.atZone(zone).toInstant();
    Date date = Date.from(instant);
}

// 07、计算2个 LocalDate 之间相差多少天，如果是同一天则会返回0
public long differLocalDateDay(LocalDate before,LocalDate after){
    LocalDate before = LocalDate.of(2017, 12, 15);
    LocalDate after = LocalDate.of(2017, 12, 15);
    long differDay = after.toEpochDay() - before.toEpochDay();
    return Math.abs(differDay);
}

// 08、就算2个 LocalDateTime 之间相差多少天，如果是同一天返回0
public long differDayOfLocalDateTime(){
    LocalDateTime first = LocalDateTime.of(2018, 8, 15, 1, 1, 1);
	LocalDateTime second = LocalDateTime.of(2018, 9, 16, 1, 5, 1);
    return Duration.between(first, second).toDays();
}