如何使用Java8中的LocalDateTime计算两个日期之间的时间差？

Question

LocalDateTime fromDateTime = LocalDateTime.of(2017, 07, 07, 07, 00, 55);
LocalDateTime toDateTime = LocalDateTime.now();
LocalDateTime tempDateTime = LocalDateTime.from(fromDateTime);

long years = tempDateTime.until(toDateTime, ChronoUnit.YEARS);
tempDateTime = tempDateTime.plusYears(years);

long months = tempDateTime.until(toDateTime, ChronoUnit.MONTHS);
tempDateTime = tempDateTime.plusMonths(months);

long days = tempDateTime.until(toDateTime, ChronoUnit.DAYS);
tempDateTime = tempDateTime.plusDays(days);

long hours = tempDateTime.until(toDateTime, ChronoUnit.HOURS);
tempDateTime = tempDateTime.plusHours(hours);

long minutes = tempDateTime.until(toDateTime, ChronoUnit.MINUTES);
tempDateTime = tempDateTime.plusMinutes(minutes);

long seconds = tempDateTime.until(toDateTime, ChronoUnit.SECONDS);

System.out.println("" + java.time.Duration.between(tempDateTime, toDateTime).toHours());

System.out.println(years + " years "
        + months + " months "
        + days + " days "
        + hours + " hours "
        + minutes + " minutes "
        + seconds + " seconds.");

return openBrat!=null 
        && openBrat.until(LocalDateTime.now(), ChronoUnit.DAYS) == 0 &&  
          openBrat.until(LocalDateTime.now(), ChronoUnit.HOURS) >= 8
         && openBrat.until(LocalDateTime.now(), ChronoUnit.Minutes) >= 0;

有人能建议如何减法吗？比如：

2017 07 06 23:30:00 - 2017 07 07 01:30:00 - Should return 2 hours.

Answer 1

下面的代码打印2，就像您所期望的那样。

LocalDateTime ldt1 = LocalDateTime.of(2017, 07, 06, 23, 30, 00);
LocalDateTime ldt2 = LocalDateTime.of(2017, 07, 07, 1, 30, 00);
System.out.println(Duration.between(ldt1, ldt2).toHours());

你的代码没有问题。如果你没有得到你期望的结果，你可能需要检查一下你的期望是否正确。

要在相差小于8小时的情况下做某事，可以这样做：

LocalDateTime ldt1 = LocalDateTime.of(2017, 07, 06, 23, 30, 00);
LocalDateTime ldt2 = LocalDateTime.of(2017, 07, 07, 1, 30, 00);
Duration d1 = Duration.between(ldt1, ldt2);
Duration d2 = Duration.ofHours(8);

if (d1.compareTo(d2) > 0) {
    System.out.println("do nothing");
} else {
    System.out.println("do something");
}