One of the new features of Mac OSX 10.7 "Lion" is the removal of Java (along with flash). Heres a quick tip on how to install it.
Open Terminal and type "java" (no quotes), and hit enter, it will state "No Java runtime present, requesting install."
up will pop the software update utility and it will download and install java for you from apple.com
There maybe another way (haven't searched) but here you go, a quick and easy way to get your morning java on Lion.