Note that if you need to install Java then you want to download the security update to protect your computer from the extant malware. And, also then see:
Helpful Links Regarding Flashback Trojan
A link to a great User Tip about the trojan: Flashback Trojan User Tip
A related link in the tip to a checker: Malware Checker Dowload Link
Another excellent reference on malware: Mac Malware Guide
A Google search can reveal a variety of alternatives on how the remove the trojan should your computer get infected. This can get you started.
For now I recommend the User Tip from etressoft to detect and remove or one of the following:
Checking for and removing the "Flashback" trojan
Kaspersky Flashback Trojan Site:Flashback Trojan Detection and Removal
F-Secure Tool: Flashback Removal Tool
Also see Apple's article About Flashback malware.
But if you don't need Java then you should be OK. Just be sure that if you download Adobe's Flashplayer, that you do so only from Adobe's website to be sure you are getting the real thing.