Windows和Unix之间的ZoneDateTime精度差异

Question

I execute the following code and I got a different precision between Windows and Unix (macOs).

import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;

public class TimeTest {

    public static void main(String[] args) {
        System.out.println(DateTimeFormatter.ISO_OFFSET_DATE_TIME.format(ZonedDateTime.now()));
    }
}

Output on MacOS ( Darwin Nicolass-MacBook-Pro.local 17.3.0 Darwin Kernel Version 17.3.0: Thu Nov 9 18:09:22 PST 2017; root:xnu-4570.31.3~1/RELEASE_X86_64 x86_64 ) is

> java -version
java version "1.8.0_162"
Java(TM) SE Runtime Environment (build 1.8.0_162-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.162-b12, mixed mode)
> java TimeTest 
2018-01-31T11:05:49.59+01:00

while on Windows

>java -version
java version "1.8.0_161"
Java(TM) SE Runtime Environment (build 1.8.0_161-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, mixed mode)

>java TimeTest
2018-01-31T11:02:22.452+01:00

Is there an expected output or a bug?

Answer 1

I suspect you just happened to run at an instant where the time was on a 10ms boundary on the Mac.

Here's some sample code to try:

import java.time.*;
import java.time.format.*;

class Test {
    public static void main(String[] args) throws Exception {
        DateTimeFormatter formatter = DateTimeFormatter.ISO_OFFSET_DATE_TIME;

        String last = "";
        while (true) {
            String next = formatter.format(ZonedDateTime.now());
            if (!last.equals(next)) {
                last = next;
                System.out.println(next);
            }
        }
    }
}

The output on my Windows box shows a mixture of output lengths. For example:

2018-01-31T10:17:34.589Z
2018-01-31T10:17:34.59Z
2018-01-31T10:17:34.591Z
2018-01-31T10:17:34.592Z
2018-01-31T10:17:34.593Z
2018-01-31T10:17:34.594Z
2018-01-31T10:17:34.595Z
2018-01-31T10:17:34.596Z
2018-01-31T10:17:34.597Z
2018-01-31T10:17:34.598Z
2018-01-31T10:17:34.599Z
2018-01-31T10:17:34.6Z
2018-01-31T10:17:34.601Z

I suspect if you run that code in your various environments, you'll see the same result.

If you need the same length for all output, I think you'll need to specify a custom pattern to DateTimeFormatter.ofPattern(String, Locale) .