New way: Make sure you have the non-free repositories in your sources.list, then:
# aptitude install sun-java5-jre sun-java5-plugin
For Flash, all I did was click OK when the browser came up saying I needed a plugin.
All this, of course applies only to 32-bit OSes, and if you actually have a new install of Etch, you should have IceWeasel instead of Firefox.
Furthermore these things have been posted many times. A simple search of the forums would have returned these answers quickly.