It is because printStackTrace
writes in System.err
while System.out.println
writes on System.out
. Even if both System.err
and System.out
use the same underlying resource for the output messages (e.g. the same file or the same console), they flush at different moments.
If you want to have a synchronized output, write the exceptions in System.out
as well:
e.printStackTrace(System.out);
Or even better, use a logger, which already synchronizes the outputs into a shared resource and give you more options about what's being output in the message e.g. Class, method, date and time, thread name, etc. among other benefits like writing log messages in database instead of a text file, and on.
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