My game says I won even before starting!

class Game {
    public static final int MAX_MISSES = 7;
    private String answer;
    private String hits;
    private String misses;

    public Game(String answer) {
        this.answer = answer.toLowerCase();
        hits = "";
        misses = "";
    }
    private char normalizeGuess(char letter) {
        if(!Character.isLetter(letter)) {
            throw new IllegalArgumentException("A letter is required");
        } 
           letter = Character.toLowerCase(letter);
           if ((hits.indexOf(letter) != -1) || misses.indexOf(letter) != -1) {
                throw new IllegalArgumentException(letter + " has already been guessed");
                }
        return letter;
     }
    public boolean applyGuess(String letters) {
        if (letters.length() == 0) {
            throw new IllegalArgumentException("No letter found");
        }
        return applyGuess(letters.charAt(0));
    }                                                     
    public boolean applyGuess(char letter) {   
        letter = normalizeGuess(letter);
        boolean isHit = answer.indexOf(letter) != -1;
        if (isHit) {
        hits += letter;
        } else {
            misses += letter;
                }
        return isHit;
    }
    public int getRemainingTries() {
        return MAX_MISSES - misses.length();
    }
    public String getCurrentProgress(){
        String progress = "";
    for (char letter : answer.toCharArray()) {
        char display = '_';
        if (hits.indexOf(letter) == -1) {
            display = letter;
            }
        progress += display;
        }
    return progress; 
    }
    public boolean isWon() {
        return getCurrentProgress().indexOf('_') == -1;
    }
    public String getAnswer() {
        return answer;
        }    

}

import java.util.Scanner;

class Prompter {
    private Game game;

    public Prompter(Game game) {
        this.game = game;
    }
    public boolean promptForGuess() {
        Scanner scanner = new Scanner(System.in);
        boolean isHit = false;
        boolean isAcceptable = false;

        do {
            System.out.print("Enter a letter:  ");
            String guessInput = scanner.nextLine();            
            try {
                isHit = game.applyGuess(guessInput);
                isAcceptable = true;
                } catch (IllegalArgumentException iae) {
                System.out.printf("%s. Please try again. %n",
                                  iae.getMessage());
                    }
        } while (!isAcceptable); 
        return isHit;   
    }
    public void displayProgress() {
        System.out.printf("You have %d remaining tries: %s%n",
                          game.getRemainingTries(),
                          game.getCurrentProgress());
    }
    public void displayOutcome() {
        if (game.isWon()) {
            System.out.printf("Congratulations! You won with %d tries remaining.%n",
                             game.getRemainingTries());
        } else {
            System.out.printf("Sorry... The answer was %s.%n",
                               game.getAnswer());
        } 
    }
}

public class Hangman {

  public static void main(String[] args) {
    // Your incredible code goes here...

    Game game = new Game("treehouse");
    Prompter prompter = new Prompter(game);
    while (game.getRemainingTries() > 0 && !game.isWon()) {
        prompter.displayProgress();
        prompter.promptForGuess();
    }
        prompter.displayOutcome();
  }
}