Summary

Clarify the ZonedDateTime#toString() documentation to avoid misunderstanding with regard to zero seconds/nanoseconds

Problem

With the current wording/example, users may misread as if seconds value is always included, even if it is zero.

Solution

Refine the wording to clearly mention they are composed using LocalDateTime#toString() which explains the omission.

Specification

Change the method description of ZonedDateTime#toString() as follows:

      * Outputs this date-time as a {@code String}, such as
      * {@code 2007-12-03T10:15:30+01:00[Europe/Paris]}.
      * <p>
-     * The format consists of the {@code LocalDateTime} followed by the {@code ZoneOffset}.
+     * The format consists of the output of {@link LocalDateTime#toString()},
+     * followed by the output of {@link ZoneOffset#toString()}.
+     * If the time has zero seconds and/or nanoseconds, they are
+     * omitted to produce the shortest representation.
      * If the {@code ZoneId} is not the same as the offset, then the ID is output.
      * The output is compatible with ISO-8601 if the offset and ID are the same,
      * and the seconds in the offset are zero.