How to replace specific word from String

Question

how can I replace a specific word from user input and display it as an asterisk. This is my code.

String[] filteredWords = ["apple", "banana", "orange"];

private String convertWord(String input) {
    StringBuilder asterisk = new StringBuilder();
    for (String filter: filteredWords) {
        if (input.toLowerCase().contains(filter)) {
            for (int i = 0; i < filter.length(); i++) {
                asterisk.append("*");
            }
            input = input.replace(filter, asterisk.toString());
        }
    }

    return input;
}

for example the user input or type "This is apple and not orange", the expected output would be "This is ***** and not ******".

but my problem here is when the user type (with a character casing) "This is Apple and not oRaNGE" or "This is aPpLe and not Orange" the output is not changing. The word apple and orange are not being replace with an asterisk.

any help is appreciated. Thank you!

Answer 1

I like using regex replacement here, with an alternation containing all your search terms:

String[] filteredWords = { "apple", "banana", "orange" };
String regex = "(?i)\\b(?:" + String.join("|", filteredWords) + ")\\b";

private String convertWord(String input) {
    input = input.replaceAll(regex, "*");
    return input;
}

convertWord("Apple watermelon ORANGE boot book pear banana");

The output from the above method call is:

* watermelon * boot book pear *

Answer 2

String[] filteredWords = ["apple", "banana", "orange"];

private static String convertWord(String input) {
        StringBuilder asterisk = new StringBuilder();
        String inputInLower = input.toLowerCase();
        for (String filter: filteredWords) {
                if (inputInLower.contains(filter)) {
                    for (int i = 0; i < filter.length(); i++) {
                        asterisk.append("*");
                    }
                    inputInLower = inputInLower.replace(filter, asterisk.toString());
                    asterisk.setLength(0);
                }
            }
            return inputInLower;
        }

There was 2 problems I found in your code

1. Your are using the input string which is not converted to lower characters, so array value is not matching. You can solve this by using a new variable as I use in answer or convert to lower before replacing.
2. Second problem was with StringBuilder you have to clear builder after every iteration or else last characters will be append in that.