Tic-Tac-Toe. Stage 3. hyperskill.org

package tictactoe;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        // write your code here
        Grid grid = new Grid();
        grid.fillGrid();
        grid.setGameInput();
        grid.checkGameState();
    }
}

class Grid{
//    Scanner s = new Scanner(System.in);
    static String input;

    public char[] field = new char[9];
    protected void fillGrid() {
        for (int i = 0; i < field.length; i++) {
                field[i] = '_';
        }
    }
    public void showGrid() {
        System.out.print("---------\n" +
                         "| " + field[0] + " " + field[1] + " " + field[2] + " |\n" +
                         "| " + field[3] + " " + field[4] + " " + field[5] + " |\n" +
                         "| " + field[6] + " " + field[7] + " " + field[8] + " |\n" +
                         "---------\n");
    }

    public void setGameInput () {
        Scanner s = new Scanner(System.in);
        input = s.nextLine();
        field = input.toCharArray();
        showGrid();
        checkGameState();
    }

    public void checkGameState() {
        int xCounter = 0;
        int yCounter = 0;

        for (int i = 0; i < field.length; i++) {
            if (field[i] == 'X') {
                xCounter++;
            } else if (field[i] == 'O') {
                yCounter++;
            }
        }
        boolean isItImpossibleQuantityDifference = xCounter > yCounter + 1 || xCounter < yCounter - 1 || yCounter > xCounter + 1 || yCounter < xCounter - 1 ? true : false;


        for (;;) {
            if ((input.contains("_") && !isXWin() && !isOWin()) && !isItImpossibleQuantityDifference) {
                System.out.println("Game not finished");
                return;
            } else if (isXWin() && !isOWin()) {
                System.out.println("X wins");
                return;
            } else if (isOWin() && !isXWin()) {
                System.out.println("O wins");
                return;
            } else if ((isOWin() && isXWin()) || isItImpossibleQuantityDifference || (isXWin() && isOWin())) {
                System.out.println("Impossible");
                return;
            } else {
                System.out.println("Draw");
                return;
            }
        }
    }

    private boolean isXWin () {
        return (field[0] == 'X' && field[4] == 'X' && field[8] == 'X') ||
            ((field[2] == 'X' && field[4] == 'X' && field[6] == 'X') ||

            (field[0] == 'X' && field[3] == 'X' && field[6] == 'X') ||
            (field[1] == 'X' && field[4] == 'X' && field[7] == 'X') ||
            (field[2] == 'X' && field[5] == 'X' && field[8] == 'X') ||

            (field[0] == 'X' && field[1] == 'X' && field[2] == 'X') ||
            (field[3] == 'X' && field[4] == 'X' && field[5] == 'X') ||
            (field[6] == 'X' && field[7] == 'X' && field[8] == 'X'));
    }
    private boolean isOWin () {
        return (field[0] == 'O' && field[4] == 'O' && field[8] == 'O') ||
               ((field[2] == 'O' && field[4] == 'O' && field[6] == 'O') ||

                (field[0] == 'O' && field[3] == 'O' && field[6] == 'O') ||
                (field[1] == 'O' && field[4] == 'O' && field[7] == 'O') ||
                (field[2] == 'O' && field[5] == 'O' && field[8] == 'O') ||

                (field[0] == 'O' && field[1] == 'O' && field[2] == 'O') ||
                (field[3] == 'O' && field[4] == 'O' && field[5] == 'O') ||
                (field[6] == 'O' && field[7] == 'O' && field[8] == 'O'));
    }

}