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 ());
