Adding Char to Char Array in Java

Question

I'm still pretty new to Java so bear with me. I'm making a simple hangman game that takes input from the user. I am trying to append the guessed letter to the knownLetters array but I get a type mismatch. I tried .concat() and got the same type error. Here is where I am now. Any ideas or documentation resources (that a novice can read) would be helpful. Thanks!

Edit: Thanks for the comments, everyone! These are very helpful.

 public static boolean updateWithGuess(char[] knownLetters,
                                      char guessedLetter,
                                      String word) {

    System.out.println(Arrays.toString(knownLetters));

    int i = 0;
    while(word.indexOf(i, guessedLetter) != -1) {
      i = word.indexOf(i, guessedLetter) + 1;
      knownLetters += guessedLetter;

Answer 1

Using arrays in that case is not the best choice because arrays have a fixed size and you cannot dynamically add and remove items, maybe rather choose lists.

If you need a simple introduction, here you are:
https://www.geeksforgeeks.org/list-interface-java-examples/

Answer 2

Others have mentioned StringBuilder and List which are a step in the right direction as they dynamic (in number of elements). However since this question is only concerned with keeping track of each letter that was guessed a set makes the most sense. One common example is HashSet . Sets do not allow duplicates. However sets will allow both the upper and lower case versions of a character to be present in the set (since they have different values). So you could normalize all the guesses and known letters to either uppercase or lowercase.