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by maccard 483 days ago
I worked on an app in kotlin a while back, and am currently working in a dotnet app. We can run our entire unit test suite faster than the JVM started up on that project.

Also, 8 seconds is quick in my experience for Java - I’ve seen more like 15-30
1 comments
winrid 483 days ago
The JVM starts in milliseconds

Probably you're loading many thousands of classes...

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mrkeen 483 days ago
It certainly tells me it does. i can hit 'run unit test', sit back in my chair and zone out for 5 seconds, then come back and read that the test took 22ms.
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PhilipRoman 482 days ago
Thanks for bringing up some painful memories. Now I'm working in C and tests take about 100ms end-to-end (multicore, no frameworks). Sometimes I re-run them for no reason just to enjoy how fast everything is.
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winrid 482 days ago
haha well your test did take 22ms, but starting the JVM and loading all the classes and all your dependency injection stuff probably took 5s. You can test it yourself with a tiny hello world, it's pretty fast to start.
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maccard 482 days ago
But that's our point - you're saying java is fast (and it is ripping fast once it gets going) and the startup is fast, unless it's not.
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winrid 482 days ago
Well no, startup is fast, period. You're probably just giving the class loader a ton of work on startup? I would start with checking that I think.

It could also be when he's hitting "run test" it's actually "compile and run"...

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maccard 482 days ago
> Well no, startup is fast, period. You're probably just giving the class loader a ton of work on startup? I would start with checking that I think.

Ok, maybe I misspoke about the "JVM" startup. But the time between `mvn test` and it actually logging the first line of user code was in the region of 15 seconds. Every java project I've worked on has had startup time issues once they're bigger than a toy project.

Saying "the JVm startup is fine, it's just the class loader that's slow" reinforces the point of "it's slow to startup"

> It could also be when he's hitting "run test" it's actually "compile and run"...

This would be true in C# too, and in go. Both of those tools have much quicker compilation times IME than java, which is just a nice plus.

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mrkeen 482 days ago
Well I could switch to a programming language that isn't so slowed down by ahead-of-time compilation. Maybe a JIT language?
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maccard 483 days ago
Yeah that’s been my experience too.
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