Here is an opensource setup that does the job as JRebel which offcourse is not free.
Download HotswapAgent latest release from this url
Download DCEVM jar from the following url
Install DCEVM as an administrator
java -jar DCEVM-light-8u112-installer.jar
Create a new run configuration in intelliJ with following VM option -XXaltjvm=dcevm -javaagent:C:\Dev\sw\HotswapAgent-0.3\hotswap-agent.jar -Xms1G -Xmx5G
Now you can modify the Java code on the fly and don’t need to restart the whole application. Just don’t forget to compile the file that you modified.
For more information