building web page content filter

Question

i want to build a filter to block pornography sites so i have some questions :

what tools i need ?

what are the algorithms i have to use ? (speed , efficient )

where i can find an open source filter ?

and i want to use java .

thanks

update : i need this filter for my project

Answer 1

Save yourself a lot of time, bother, false positives and false negatives by using OpenDNS

Answer 2

There are a LARGE number of tools that already do this. Are you sure you want to reinvent this wheel?

If so, the easiest (not necessarily the most efficient) is to create a proxy server that blocks content you want to block.

Building a Java proxy server has already been discussed on StackOverflow, Write HTTP proxy in Java