Re-Enable Apple Java 6 SE from Command Line? So, I broke Java Preferences.app.  I'm on Mountain Lion. I had Java 6 SE (the Apple-distributed JDK/JRE) and Oracle's Java 7u10 preview. Trying to get a stub app to launch with Java 7, I unchecked the Java 6 SE checkboxes in Java Preferences.app. Now not only will my stub app not launch, but Java Preferences.app won't launch (it says there's no valid JRE 1.4+ available).  I understand this is probably because Apple's Java launcher stub is not compatible with 7u10 -- not sure how to manually re-enable SE 6, though.
Two things are needed worst case (and assuming you are still on 10.6 Snow Leopard):


Re-download the SE 6 and install it
Manually enable browser plug in if you care to have that functionality:



 ln -sf /System/Library/Java/Support/Deploy.bundle/Contents/Resources/JavaPlugin2_NPAPI.plugin "/Library/Internet Plug-Ins/JavaAppletPlugin.plugin"
 ln -sf /System/Library/Frameworks/JavaVM.framework/Commands/javaws /usr/bin/javaws



There is great coverage of the how and why I came up with these steps from Rich Trouton's blog:


Re-enable the Apple Java 6 plug-in for use with web browsers
Java for OS X 2012-006 and Java for Mac OS X 10.6 Update 11


Apple also has similar steps in their KB article about the move from SE 6 to 7 here:


Java for OS X 2012-006: How to re-enable the Apple-provided Java SE 6 applet plug-in and Web Start functionality