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From: Cecil Westerhof <Cecil@decebal.nl>
Newsgroups: comp.lang.java.programmer
Subject: Re: Starting jshell takes about 15 seconds
Date: Mon, 29 Jul 2019 20:45:28 +0200
Organization: Decebal Computing
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Andreas Leitgeb <avl@logic.at> writes:

> Arne Vajhøj <arne@vajhoej.dk> wrote:
>> On 7/28/2019 12:04 PM, Cecil Westerhof wrote:
>>> I have played with jshell before, but at the moment I am a bit more
>>> serious with it. Starting jshell between 15 and 20 seconds. Executing
>>> /reset takes 7 to 10 seconds.
>>> This seems a bit long to me. For example starting ipython3 takes less
>>> as two seconds. Is this normal, or is there a problem with my system?
>>> I am working with Debian 9.
>> Here starting jshell takes 1-3 seconds depending on the
>> system. Windows 7 and Ubuntu 18.04 both with Java 11.
>
> The machine's RAM and # of cores may be more significant here
> than the OS or even the CPU or bogomips.
>
> (And in case of enough RAM, then also whether jshell is already
> in the cache versus first-start.)
>
> PS: Ubuntu here with 8GB on core i7 2.80GHz (HW about 10 years old):
>   first jshell start: roughly 6 secs, second one roughly 2 secs
>
> $ time $JAVA12_HOME/bin/jshell <<< "/exit"

My startup is expensive. When doing it like that I get a real around 9
seconds, but when I use:
    time jshell --no-startup <<< /exit

real is between 1.5 and 2 seconds.

I only do:
    import java.text.DateFormat;
    import java.text.SimpleDateFormat;


    DateFormat dateTimeFormat = new SimpleDateFormat("yyyy-mm-dd HH:mm:ss");


    String currentDateTime() {
        return dateTimeFormat.format(new Date());
    }


    println(currentDateTime());

But it seems it is quit expensive. :'-(

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof