Hangman Java

import java.util.*;

public class helloWorld {

    private static final Character EMPTY_CHAR = 0;

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        // get the secret word
        System.out.println("Input Secret Word:");
        String secretWord = input.nextLine();

        int lives = 10;
        // list of guessed characters
        ArrayList<Character> lettersGuessed = new ArrayList<Character>();

        // play the game until no remaining lives
        while (lives > 0) {
            System.out.println("you have " + lives + "left.");
            System.out.println("Available letters: " + getRemainingPossibleLetters(lettersGuessed));
            System.out.print("please guess a letter: ");

            // get a guess character
            Character guessedLetter = input.nextLine().charAt(0);

            // check is already guessed, continue loop if yes
            if (lettersGuessed.contains(guessedLetter)) {
                System.out.println("Oops! You've already guessed that letter");
                continue;
            }

            // add to list of guessed characters
            lettersGuessed.add(guessedLetter);

            // get word progress
            String wordProgress = getWordProgress(secretWord, lettersGuessed);

            // check if char is in secret word
            if (isCharInWord(secretWord, guessedLetter)) {
                System.out.println("Good Guess: " + wordProgress);
                if (checkGameWon(secretWord, lettersGuessed)) {
                    // if game won, break from loop
                    break;
                } else {
                    // contine loog if not won
                    continue;
                }
            } else {
                // loose life if not in secret word
                lives--;
                System.out.println("Oops! wrong guess: " + wordProgress);
            }
        }

        if (lives > 0) {
            // won the game with remaining lives > 0
            System.out.println("Congrats!!");
        } else {
            // game lost
            System.out.println("Game Over!");
        }

    }

    /**
     * returns a boolean True if all the letters in secretWord are in lettersGuessed
     * loop through the letters of secretWord.
     *
     * @param secretWord
     * @param lettersGuessed
     * @return
     */
    static boolean checkGameWon(String secretWord, ArrayList<Character> lettersGuessed) {
        // replace guessed chars in secret word by space
        for (Character c : lettersGuessed) {
            secretWord = secretWord.replace(c, EMPTY_CHAR);
        }
        // remove spaces
        secretWord = secretWord.trim();

        // if secret word is "", the game is won
        return secretWord.length() == 0;
    }

    /**
     * how much of the word returns String comprised of letters and underscores
     * which represent letters not yet guessed in secretWord
     *
     * @param secretWord
     * @param lettersGuessed
     * @return
     */
    static String getWordProgress(String secretWord, ArrayList<Character> lettersGuessed) {
        String result = "";

        for (int i = 0; i < secretWord.length(); i++) {
            if (lettersGuessed.contains(secretWord.charAt(i))) {
                result += secretWord.charAt(i);
            } else {
                result += "_";
            }
            result += " ";
        }
        return result;
    }

    /**
     * letters left returns String comprised of letters that have not yet been
     * guessed the letters should appear in alphabetical order
     *
     * @param lettersGuessed
     * @return
     */
    static String getRemainingPossibleLetters(ArrayList<Character> lettersGuessed) {
        String remaining = "abcdefghijklmnopqrstuvwxyz";

        for (Character c : lettersGuessed) {
            remaining = remaining.replace(c, EMPTY_CHAR);
        }

        return remaining;
    }

    /**
     * return true is secretWord contains guessed letter
     *
     * @param secretWord
     * @param guessedLetter
     * @return
     */
    static boolean isCharInWord(String secretWord, Character guessedLetter) {

        // here we replace (if available) guessed letter in secret word
        // by an empty char, resulting word would not be equal to secret word
        // example: secretWord = test -- --
        // guessedLetter = 't' -->
        // result= true (resulting word :"es" not equal "test")
        // guessedLetter = 'a' -->
        // result= false (resulting word: "test" equal "test")
        return !secretWord.equals(secretWord.replace(guessedLetter, EMPTY_CHAR));
    }

}