I have JDownloader and other .jar files. Upon double-clicking them, nothing happens. Not even an icon in the dock. my "java -version" command returns this: java version "1.7.0_09" Java(TM) SE Runtime Environment (build 1.7.0_09-b05) Java HotSpot(TM) 64-Bit Server VM (build 23.5-b02, mixed mode) If I go to the Java System Preferences app it says I have Java 1.7.0_21 installed. I've tried variations of the terminal command "Java Version 1.7.0_21" but I just get "Error: Could not find or load main class Version" Is there anything I can do to tell my Mac to use RE 1.7.21? I only have 1.7.21 listed in my Java Preferences as installed Java Runtime Environments.