如何计算两个Java java.sql.Timestamps之间的差异？

Question

请包括nanos，否则将是无关紧要的：

long diff = Math.abs(t1.getTime () - t2.getTime ());

[编辑]我想要最精确的结果，所以不要双打；仅整数/长算术。同样，结果必须是肯定的。伪代码：

Timestamp result = abs (t1 - t2);

例子：

t1 = (time=1001, nanos=1000000), t2 = (time=999, nanos=999000000)
 -> diff = (time=2, nanos=2000000)

是的，在java.sql.Timestamp中毫秒被复制的时间和毫微秒不相上下，所以1001个毫秒装置1秒（1000）和1毫这是在time部件和nanos部分，因为1毫秒=
1000000毫微秒）。这比看起来要狡猾得多。

我建议不要在未实际测试代码或未准备好工作代码示例的情况下发布答案：）

Answer 1

经过一个小时的各种单元测试，我想到了以下解决方案：

public static Timestamp diff (java.util.Date t1, java.util.Date t2)
{
    // Make sure the result is always > 0
    if (t1.compareTo (t2) < 0)
    {
        java.util.Date tmp = t1;
        t1 = t2;
        t2 = tmp;
    }

    // Timestamps mix milli and nanoseconds in the API, so we have to separate the two
    long diffSeconds = (t1.getTime () / 1000) - (t2.getTime () / 1000);
    // For normals dates, we have millisecond precision
    int nano1 = ((int) t1.getTime () % 1000) * 1000000;
    // If the parameter is a Timestamp, we have additional precision in nanoseconds
    if (t1 instanceof Timestamp)
        nano1 = ((Timestamp)t1).getNanos ();
    int nano2 = ((int) t2.getTime () % 1000) * 1000000;
    if (t2 instanceof Timestamp)
        nano2 = ((Timestamp)t2).getNanos ();

    int diffNanos = nano1 - nano2;
    if (diffNanos < 0)
    {
        // Borrow one second
        diffSeconds --;
        diffNanos += 1000000000;
    }

    // mix nanos and millis again
    Timestamp result = new Timestamp ((diffSeconds * 1000) + (diffNanos / 1000000));
    // setNanos() with a value of in the millisecond range doesn't affect the value of the time field
    // while milliseconds in the time field will modify nanos! Damn, this API is a *mess*
    result.setNanos (diffNanos);
    return result;
}

单元测试：

    Timestamp t1 = new Timestamp (0);
    Timestamp t3 = new Timestamp (999);
    Timestamp t4 = new Timestamp (5001);
    // Careful here; internally, Java has set nanos already!
    t4.setNanos (t4.getNanos () + 1);

    // Show what a mess this API is...
    // Yes, the milliseconds show up in *both* fields! Isn't that fun?
    assertEquals (999, t3.getTime ());
    assertEquals (999000000, t3.getNanos ());
    // This looks weird but t4 contains 5 seconds, 1 milli, 1 nano.
    // The lone milli is in both results ...
    assertEquals (5001, t4.getTime ());
    assertEquals (1000001, t4.getNanos ());

    diff = DBUtil.diff (t1, t4);
    assertEquals (5001, diff.getTime ());
    assertEquals (1000001, diff.getNanos ());

    diff = DBUtil.diff (t4, t3);
    assertEquals (4002, diff.getTime ());
    assertEquals (2000001, diff.getNanos ());