I have exactly the same error. I tried with JDK 8 and JDK 12, and I still have have the same problem.I checked the version of java on my mac, and here is what I have :

Last login: Fri Jul 5 15:21:40 on console
Mac-Pro-de-Lydia:~ LD$ /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/bin/java -version
java version “1.8.0_211”
Java(TM) SE Runtime Environment (build 1.8.0_211-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.211-b12, mixed mode)
Mac-Pro-de-Lydia:~ LD$ java -version
java version “12.0.1” 2019-04-16
Java(TM) SE Runtime Environment (build 12.0.1+12)
Java HotSpot(TM) 64-Bit Server VM (build 12.0.1+12, mixed mode, sharing)
Mac-Pro-de-Lydia:~ LD$

When I try to open Icy 2: I have this error message

Last login: Fri Jul 5 15:25:45 on ttys001
/Applications/Install\ Central/Icy-2019/icy\ 2.app/icy ; exit;
Mac-Pro-de-Lydia:~ LD$ /Applications/Install\ Central/Icy-2019/icy\ 2.app/icy ; exit;
usage: dirname path
Error: Unable to access jarfile /updater.jar
logout
Saving session…
…copying shared history…
…saving history…truncating history files…
…completed.

[Opération terminée]

I tried to unlock the file by typing my admin root, but I have still that bug.

Then I tried to lauch and old version of Icy, and then it crash because of the java that is not any more compatible…