It is fair to say that Oracle is not treating Java well. After the Ask-bar annoyance it is now bugging Java users with a faulty installation of the recent Java update. No surprise that Java loses more and more ground. Java was designed to be safer than native applications and easier to install and maintain. And it could have been the solution to many problems of current computer industry. But the contrary has happened, due to mistakes in the upper floors of Sun, Microsoft, Apple and recently Oracle, just to name the main players. The bashing of the Linux community was not helpful either.
Back to the recent problem for Java on Windows (maybe on Mac too): Oracle now introduces an incorrect link into the system path. While this link works in the command line it does not work for desktop items and associated files.
The first solution is to fix this link. Go to the system settings and search for the system variables. Replace the path to Java with the correct path („C:\Program Files\Java\jdk1.8.0_51\bin“ on my computer). Unfortunately, this path contains the Java version number. So you have to change this with every update.
For C.a.R., I have chosen another solution. To get the desktop icon working, I link to the jar file directly. Moreover, the link gets the proper icon for C.a.R. In earlier versions, I linked to javaw.exe which started the jar file. For the association of files to C.a.R., I associate to a batch file which calls javaw.exe. The path to the jar file must be contained in this call. Thus I create the batch file during the installation with another batch file.