Can't open JAR files - tried everything

Question

Hi guys.
So, I have this problem that I can' open .jar files. I'm getting this: "Java JAR-file could not start"
I have literally tried EVERYTHING.
This is what I have tried:
Uninstall, reinstall, restart Mac between every installation, have newest Java now (Java Standard Edition. Version 7 Update 67 (build 1.7.0_67.b01).
Tried this command: java -jar myfile.jar. This results in Unable to access .jarfile
Have googled and found a recent thread about this here on apple forum which lead to following this tutorial on YouTube: https://www.youtube.com/watch?v=lV3npU1NbHQ&feature=youtu.be&html5=1 which did not work either.
Console does not give me much when I try to open, but one time I got this:
04.10.14 00:01:48,571 java[554]: objc[554]: Class JavaLaunchHelper is implemented in both /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/bin/java and /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/lib/jli/./libjli.dylib. One of the two will be used. Which one is undefined.
PLEASE help guys! I'm dying, this is so annoying, I really need to open the file.
Thanks in advance!

Answer 1

same happens with Yosemite (10.10)
double clicking on a jar file I get 'The java JAR file "forge-1.7.10-10.13.2.1231-universal.jar" could not be launched'
if I try javaws -viewer
I get:
objc[12654]: Class JavaLaunchHelper is implemented in both /Library/Internet Plug-ins/JavaAppletPlugin.plugin/Contents/Home/bin/java and /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/lib/jli/./libjli.dylib. One of the two will be used. Which one is undefined.
if I remove the library /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/lib/jli/./libjli.dylib the message disappears but still is impossible to run jar files
if I remove /Library/Internet Plug-ins/JavaAppletPlugin.plugin/Contents/Home/bin/java nothing happens anymore.
embarassing situation...