You can find all the details here:
- IDEA-170117 “objc: Class JavaLaunchHelper is implemented in both …” warning in Run consoles
The message is benign, there is no negative impact from this problem since both copies of that class are identical (compiled from the exact same source). It is purely a cosmetic issue.
If it annoys you or affects your apps in any way (it shouldn’t), the workaround for IntelliJ IDEA is to disable
idea_rt launcher agent by adding
Edit Custom Properties...). The workaround will take effect on the next restart of the IDE.
I don’t recommend disabling IntelliJ IDEA launcher agent, though. It’s used for such features as graceful shutdown (Exit button), thread dumps, workarounds a problem with too long command line exceeding OS limits, etc. Losing these features just for the sake of hiding the harmless message is probably not worth it, but it’s up to you.