Appropriate java software for my computer. How and where can I get it?

Java Downloads for All Operating Systems - Sun Microsystems

If you are running a Windows operating System (XP, Vista, 7), you can download the latest version of Java from this site:
http://www.java.com/en/

If you are running a Mac operating System, your computer should already have Java installed (as Mac creates and releases their own updates of Java specific to each operating system). If you believe that your version of Java is an odd or corrupted state, you may need to try an archive and reinstall to fix the problem. For more information, you should refer to this article on Apple's website at http://support.apple.com/kb/HT1710?viewlocale=en_US.