It's the go to fix for .jar file association issues, 100% clean, and has been used many times on this forum.
What aspect are you suspicious about?
If you'd rather not run it, open notepad, leave the page blank and go to File -> Save as and
Save as type: All Files (*.*) File name: temp.exe
Go to a .jar file, right click and select Open with, on the resulting dialog tick Always use the app to open .jar files
Click More apps -> Look for another app on this PC, then browse to, and select temp.exe
Now delete temp.exe
Your jar file association will be back to nothing.