How can I create a method that evaluates two variables from main class?

I have to create a program in which the user has to guess a number from 1 to 10, teacher asked us to create 6 methods: one to generate random numbers, other to check that the answer the user gives and the random number are the same, etc) I'm doing the method in which the input and random number has to be the same but I'm not sure I'm doing it correctly:

public class Guessgame {   
    static int a;
    static int a1;
    static int a2;
    static int b;

    public static void main(String[] args) {
        Scanner input = new Scanner (System.in); // User input

        b = generator(); //declara el numero aleatorio generado en "generator()"

        System.out.println("Welcome to a game, you have to guess a number between 1 to 10");
        System.out.println("You have three tries");

        System.out.println(b);

        System.out.println("What is your first guess?");

        a = input.nextInt(); //declara el numero que declaro el usuario

        evaluator();   
                                 
    }

And here's the evaluator method:

        public static void evaluator(){
        if ( a == b ){
            System.out.println("Good");                
        }
        else{
            System.out.println("Bad");
        }
    }

I just had to change evaluator(); to evaluator(a, b);

It's showing "Good", because the local variables a and b that are being initialized are different from the fields (or instance variables) a and b that are being compared. Here is a good explanation of the different types of variables in Java.

In your code, int b = generator(); is creating a local variable named b. Likewise, int a = input.nextInt(); is creating a local variable named a. To fix this, remove the data type in these statements. This will change the statements from a declaration (creating a new variable) to an initialization (setting the value of a pre-existing variable).

Also, you actually cannot reference instance variables from a static method. You would need to convert the instance variables into class variables using the static modifier.

Your new code should look like this:

public class Guessgame {   
    static int a;
    static int a1;
    static int a2;
    static int b;

    public static void main(String[] args) {
        Scanner input = new Scanner (System.in); // User input

        b = generator(); //declara el numero aleatorio generado en "generator()"

        System.out.println("Welcome to a game, you have to guess a number between 1 to 10");
        System.out.println("You have three tries");

        System.out.println(b);

        System.out.println("What is your first guess?");

        a = input.nextInt(); //declara el numero que declaro el usuario

        evaluator();   
                                 
    }

Also, your evaluator() method always prints "Good" because it was comparing the instance variables (which were never initialized, so both of them were always 0).

I would convert your evaluator() method to a FUNCTION, and make it RETURN true/false via the boolean data type. Furthermore, you can make it receive the two values as PARAMETERS:

public static boolean evaluator(int value1, int value2) {
    return value1 == value2;
}

Now, back in main(), you pass in a and b, then print either "Good" or "Bad" based on the returned results:

if (evaluator(a, b)) {
    System.out.println("Good");                
}
else {
    System.out.println("Bad");                
}

Doing it this way also means that your a and b variables could have remained local to main(), and not changed to static members of the class.