从`java.time.Instant`到`java.util.Date`的转换添加了UTC偏移量

Question

I seem to misunderstand java.util.Date 's conversion from and to java.time.Instance . I have some legacy code I need to ineract with, and this code uses java.util.Date in its API.

I am slightly confused when offsets are added in the Date API. It was my understand that Date is a UTC time ("the Date class is intended to reflect coordinated universal time (UTC)"), but when I create a Date from an Instant an offset is added:

public class TestDateInstant {
    @Test
    public void instantdate() {
        Instant i = Instant.now();
        System.out.println(i);
        Date d = Date.from(i);
        System.out.println(d);

        assertThat(i, equalTo(d.toInstant()));
    }
}

The assertion holds, but the output on the console is:

2017-09-26T08:24:40.858Z 
Tue Sep 26 10:24:40 CEST 2017

I am wondering why Date.from uses an offset in this case.

Answer 1

Date or Instant both are NOT specific to a timezone. The difference is when you print them.

Instant.toString() prints in ISO-8601 representation in UTC timezone.

Date.toString() prints it in your current timezone.

That's why you see the difference.