String.format、long 和 DateTime 转换

如果问题是重复的，我很抱歉，我没有通过谷歌找到任何东西。

对于我的问题：

我有以下测试：

public void testSecondsToMinutes() {
    long zero = 0;
    long thirty_seconds = 30;
    long one_minute = 60;
    long thirty_minutes_fiftynine_seonds = 1859;
    long two_hours_ten_miutes_fourty_seconds = 7840;

    String format1 = "00:00:00";
    String format2 = "00:00:30";
    String format3 = "00:01:00";
    String format4 = "00:30:59";
    String format5 = "02:10:40";

    assertEquals(format1,Entrypoint.secondsToMinutes(zero));
    assertEquals(format2,Entrypoint.secondsToMinutes(thirty_seconds));
    assertEquals(format3,Entrypoint.secondsToMinutes(one_minute));
    assertEquals(format4,Entrypoint.secondsToMinutes(thirty_minutes_fiftynine_seonds));
    assertEquals(format5,Entrypoint.secondsToMinutes(two_hours_ten_miutes_fourty_seconds)); 
}

以及以下函数：

public static String secondsToMinutes(long seconds)
{
    return String.format("%TH:%TM:%TS", seconds, seconds, seconds);
}

Java 文档格式化程序 https://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#dt陈述如下：

The following conversion characters are used for formatting common date/time compositions.
This conversion may be applied to long, Long, Calendar, and Date.
[...]
'R' '\u0052'    Time formatted for the 24-hour clock as "%tH:%tM"
'T' '\u0054'    Time formatted for the 24-hour clock as "%tH:%tM:%tS".

但是，我收到以下 ComparisionFailure：

expected 00:00:00 but was 01:00:00

我一定在这里遗漏了一些明显的东西......

当你通过一个long to String.format，它被解释为从纪元开始的毫秒数，这与您预期的从午夜开始的秒数是完全不同的实体。

通过直接编码您的意图，您的问题可以最简单地解决：

public static String secondsToTwentyFourHourString(long seconds) {
    return String.format("%1$TH:%1$TM:%1$TS", LocalTime.ofSecondOfDay(seconds));
}

这样，您就可以指定不依赖于时区的操作。

同样的逻辑也适用于DateTimeFormatter:

public static String secondsToTwentyFourHourString(long seconds) {
    return LocalTime.ofSecondOfDay(seconds)
        .format(DateTimeFormatter.ofPattern("HH:mm:ss"));
}