Objc[63766] Class JavaLaunchHelper is implemented in both ... and ...,One of the two will be used. Which one is undefined.

Root cause:

When starting a java application, IDEA finds two classpaths in current lcoal environment, as a result, it selects one of them and raise a waring saying above info.

To solve this problem:

1) Make sure that your local machine environment is well configured, use Mac as example:

1.1) vi ~/bash_profile
1.2) Make sure java executable applications can be find, as following:

JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_102.jdk/Contents/Home
M2_HOME=/Library/apache-maven-3.5.4
PATH=$JAVA_HOME/bin:$PATH:$M2_HOME/BIN:.
CLASSPATH=$JAVA_HOME/lib/tools.jar:$JAVA_HOME/lib/dt.jar:.
export JAVA_HOME
export PATH
export CLASSPATH
 

1.3) Run following command to make this environment variables come into play.
source ~/.bash_profile

2) Use this path to find 'custom properties':

IDEA > Help > Edit custom properties... and then add following statement at the end of the file:

idea.no.launcher = true

Then as the last step, you'll need to restart your IDEA, after that, you'll find this warning won't show any longer.