Comment 9 for bug 212207

Java2-runtime is a virtual package and it "doesn't exist"

Quote from Debian policy (http://www.debian.org/doc/debian-policy/ch-binary.html#s-virtual_pkg):

"Sometimes, there are several packages which offer more-or-less the same functionality. In this case, it's useful to define a virtual package whose name describes that common functionality. (The virtual packages only exist logically, not physically; that's why they are called virtual.) The packages with this particular function will then provide the virtual package. Thus, any other package requiring that function can simply depend on the virtual package without having to specify all possible packages individually. "

This means you "have" java2-runtime if you have one of following packages:
gij-4.1
j2re1.4
java-gcj-compat
openjdk-6-jre
sun-java5-jre
sun-java6-jre