Simple profanity filter written in Java for efficient comparison. Runtime grows based on string input, not list size.

Efficient Bad Word Filter

    static Map<String, String[]> words = new HashMap<>();
    
    static int largestWordLength = 0;
    
    public static void loadConfigs() {
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(new URL("https://docs.google.com/spreadsheets/d/1hIEi2YG3ydav1E06Bzf2mQbGZ12kh2fe4ISgLg_UBuM/export?format=csv").openConnection().getInputStream()));
            String line = "";
            int counter = 0;
            while((line = reader.readLine()) != null) {
                counter++;
                String[] content = null;
                try {
                    content = line.split(",");
                    if(content.length == 0) {
                        continue;
                    }
                    String word = content[0];
                    String[] ignore_in_combination_with_words = new String[]{};
                    if(content.length > 1) {
                        ignore_in_combination_with_words = content[1].split("_");
                    }

                    if(word.length() > largestWordLength) {
                        largestWordLength = word.length();
                    }
                    words.put(word.replaceAll(" ", ""), ignore_in_combination_with_words);

                } catch(Exception e) {
                    e.printStackTrace();
                }

            }
            System.out.println("Loaded " + counter + " words to filter out");
        } catch (IOException e) {
            e.printStackTrace();
        }

    }


    /**
     * Iterates over a String input and checks whether a cuss word was found in a list, then checks if the word should be ignored (e.g. bass contains the word *ss).
     * @param input
     * @return
     */
     
    public static ArrayList<String> badWordsFound(String input) {
        if(input == null) {
            return new ArrayList<>();
        }

        // don't forget to remove leetspeak, probably want to move this to its own function and use regex if you want to use this 
        
        input = input.replaceAll("1","i");
        input = input.replaceAll("!","i");
        input = input.replaceAll("3","e");
        input = input.replaceAll("4","a");
        input = input.replaceAll("@","a");
        input = input.replaceAll("5","s");
        input = input.replaceAll("7","t");
        input = input.replaceAll("0","o");
        input = input.replaceAll("9","g");
        

        ArrayList<String> badWords = new ArrayList<>();
        input = input.toLowerCase().replaceAll("[^a-zA-Z]", "");

        // iterate over each letter in the word
        for(int start = 0; start < input.length(); start++) {
            // from each letter, keep going to find bad words until either the end of the sentence is reached, or the max word length is reached. 
            for(int offset = 1; offset < (input.length()+1 - start) && offset < largestWordLength; offset++)  {
                String wordToCheck = input.substring(start, start + offset);
                if(words.containsKey(wordToCheck)) {
                    // for example, if you want to say the word bass, that should be possible.
                    String[] ignoreCheck = words.get(wordToCheck);
                    boolean ignore = false;
                    for(int s = 0; s < ignoreCheck.length; s++ ) {
                        if(input.contains(ignoreCheck[s])) {
                            ignore = true;
                            break;
                        }
                    }
                    if(!ignore) {
                        badWords.add(wordToCheck);
                    }
                }
            }
        }


        for(String s: badWords) {
            System.out.println(s + " qualified as a bad word in a username");
        }
        return badWords;

    }

    public static String filterText(String input, String username) {
        ArrayList<String> badWords = badWordsFound(input);
        if(badWords.size() > 0) {
            return "This message was blocked because a bad word was found. If you believe this word should not be blocked, please message support.";
        }
        return input;
    }
    
    
    

thank you @PimDeWitte - this was helpful to me.

heads up in case this is helpful to anyone else - here's how I did a copy/paste/edit of this code to integrate it into a Spring Boot application (to censor input provided by user via an MVC form): https://github.com/ILMServices/FantasyFootball/commit/dc487b4

Love it!

what's variable "words"? it's not defined

@hayderma Map<String, String[]> words = new HashMap<>();

Copy pasted and implemented for small java application with Test class : https://github.com/souwoxi/Profanity

Copy pasted and implemented for small java application with Test class : https://github.com/souwoxi/Profanity
its not work

String inputToReturn = input;
for (String swearWord : badWordsFound) {
char[] charsStars = new char[swearWord.length()];
Arrays.fill(charsStars, '*');
final String stars = new String(charsStars);

  // The "(?i)" is to make the replacement case insensitive.
  inputToReturn = inputToReturn.replaceAll("(?i)" + swearWord, stars);
}

its not return result

Using Google Docs is great.

@jolson490 Your git link is not working. I would really like to check your implementation as I am working on a spring project that needs some input filter :)

Hey guys, didn't realize people actually use this. Here's the link to the background and the tutorial: https://pimdewitte.me/2016/05/28/filtering-combinations-of-bad-words-out-of-string-inputs/

I know it has been a while, but is there a way to replace the swear word with stars and return the full message. @PimDeWitte
Similar to what @souwoxi did but instead of having no spaces, keeping the spaces and punctuation.

I improved performance of this by over a magnitude and completely eliminated garbage (allocations) 😄

https://gist.github.com/Jire/4aa72bd3554cdccdc369c216a230ee56

please can I get the code with spring boot application

anyone help me to fix this... make a **** combination of two words of one for example(f*** you) change to (**** ***) like these