Try the "tab" key to move to ok and then "enter"...?
I assume you actually want the java web browser plugin and JRE - and not the JDK (for developers)? I say this because, you're actually installing the JRE by the looks of it.
It would help if you gave details of what you're trying to do? If you're after a java browser plugin then just installing the JRE won't be enough. The JRE will be installed as a dependency of sun-java6-plugin anyway - is this what you're trying to install? If not, do following as root
Code:
aptitude install sun-java6-plugin