String Censoring

Question

I'm attempting to censor certain words from being chatted in a game. The only issue is that the player can void my censor by adding onto the words. Here's an example.

    //Check for rude words before sending to server
    List<String> tokens = new ArrayList<String>();
    tokens.add("bilbo");
    tokens.add("baggins");
    tokens.add("in");
    tokens.add("the");
    tokens.add("shire");

    String patternString = "\\b(" + StringUtils.join(tokens, "|") + ")\\b";
    Pattern pattern = Pattern.compile(patternString);
    Matcher findRudeWords = pattern.matcher(result.toLowerCase());

    while (findRudeWords.find()) {
        //Replace the bad word with astericks
        String asterisk = StringUtils.leftPad("", findRudeWords.group(1).length(), '*');
        result = result.replaceAll("(?i)" + findRudeWords.group(1), asterisk);
    }

The standing issue is that if someone said bilbobaggins, without a space in between, my censor can be easily avoided. How is it that I can make a sufficient censor that doesn't just check words?

Answer 1

Take out the two word boundaries. The two \b's. I didn't want to bother with the extra library needed for StringUtils, so I modified your code a little, but here's what I tested with:

import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.*;

class Ideone {
    public static void main(String[] args) throws java.lang.Exception {
        // Check for rude words before sending to server
        String result = "heres bilbobaggins haha";
        String patternString = "(bilbo|baggins|in|the|shire)";
        Pattern pattern = Pattern.compile(patternString);
        Matcher findRudeWords = pattern.matcher(result.toLowerCase());

        while (findRudeWords.find()) {
            // Replace the bad word with asterisks
            result = result.replaceAll("(?i)" + findRudeWords.group(1), "*");
        }
        System.out.println("result=" + result);
    }

}

Output:

result=heres ** haha

And you can play with that here: http://ideone.com/72SU7X