FULL PRODUCT VERSION :
Java SE 7 update 4 developer preview

ADDITIONAL OS VERSION INFORMATION :
Windows 7 Ultimate Service Pack 1 64-bit

A DESCRIPTION OF THE PROBLEM :
This version of the program, as well as future versions (JRE8, to name one) do not set file associations for JAR files. This can be a problem if the JAR is executable.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The JRE should be set to open JAR files, like version 7u2.
ACTUAL -
No file association.

REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
A possible workaround is to set the file association manually, but I don't know exactly what binary is used for this particular action.