Cannot find symbol error. Classes saved in different java files.

public class battleship {

int [] locationCells;
int numOfHits = 0;

//locs ist eine Platzhalter-Variable
public void setLocationCells (int [] locs) {

    locationCells = locs;
}

public String checkYourself(String stringGuess) {

    //convert an inputted String ("2" in this case) to an Integer //stringGuess ist eine Platzhalter-Variable
    int guess = Integer.parseInt(stringGuess);
    String result = "miss";

        //loop geht durch das Array --> jedes Mal wird das nächste Element des Arrays in der Variable cell abgelegt
        for (int cell : locationCells) {

            if (guess == cell) {
                result = "hit";
                numOfHits++;
                //es ist ein Treffer--> den loop verlassen; neuen guess des users erwarten
                break;
            }
         }
        //wenn die Anzahl der Treffer der Länge des Arrays entspricht, dem das Objekt b zugeorndet ist, wird result zu "kill" geändert
         if (numOfHits == locationCells.length) {
            result = "kill";
         }
        //display the result to the user
         System.out.println(result);

         return result;         //Frage: Was passiert hier?
    }
}

import java.io.*;
public class gameHelper {
    public String getUserInput (String prompt) {
        String inputLine = null;
        System.out.print (prompt + " ");
        try {
            BufferedReader is = new BufferedReader(
            new InputStreamReader(System.in));
            inputLine = is.readLine();
            if (inputLine.length() == 0) return null;
            } catch (IOException e) {
            System.out.println("IOException: " + e);
        }
        return inputLine;
    }
}

public class battleshipGame {
    public static void main(String[] args) {

        int numOfGuesses = 0;

        //holds a method for getting input the user types in the command line
        gameHelper helper = new gameHelper();

        //create a battleship object
        battleship b = new battleship();

        //create a random number from 0 to 4.999, transform it from double to int and round it down by (int) --> no decimals
        int randomNum = (int) (Math.random() * 5);

        //random number is used to make an int array for the location of the Battleship (3 consecutive ints out of 7) --> now the battleship is always on an other spot
        int[] locations = {randomNum, randomNum + 1, randomNum + 2};

        b.setLocationcells(locations);

        //create a variable to end the prompt-loop when the user killed the boat
        boolean isAlive = true;

        while (isAlive == true) {
            //method of the gamehelper class that asks the user for commandline input, reads it in after the user hits return and gives back the result in a string
            String guess = helper.getUserInput("enter a number");
            String result = b.checkyourself(guess);
            numOfGuesses++;

            if (result.equals("kill")) {
                isAlive = false;
                System.out.println("You took " + numOfGuesses + " guesses");

            }
        }
    }
}