Question

Hi, I am a student in college who is trying to make a tic tac toe game on Java. Basically, we have to make our own game, even ones that already exist, on Java. We also have to implement an interface, that I have no idea exactly. The professor also stated we need at least 2 different data structures and algorithms for the code. The professor said we could use code online, we'd just have to make some of our own adjustments, which is what I did, I just need to make my own adjustments later. I just need some help or maybe even suggestions on what exactly my tic tac toe game code should be like. I'm sorry for being a bit stupid and I know this question may sound complicated, but I really need all the help I can get. I failed one class last semester and I do not plan on failing another class this semester. So please help....I really need it. Thank you very much. My code is right below.

import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.Scanner;

public class TicTacToe implements Game {

public boolean playGame(Player player) {

static Scanner in;
static String[] board;
static String turn;

public static void main(String[] args) {

  in = new Scanner(System.in);
  board = new String[9];
  turn = "X";

  String winner = null;
  populateEmptyBoard();

  System.out.println("Welcome to 2 Player Tic Tac Toe.");

  printBoard();

  System.out.println("X's will play first. Enter a slot number to place X in:");

  while (winner == null) {
   int numInput;

   try {
    numInput = in.nextInt();
   if (!(numInput > 0 && numInput <= 9)) {
     System.out.println("Invalid input; re-enter slot number:");
     continue;
    }

   } catch (InputMismatchException e) {
    System.out.println("Invalid input; re-enter slot number:");
    continue;
   }

   if (board[numInput-1].equals(String.valueOf(numInput))) {
    board[numInput-1] = turn;

    if (turn.equals("X")) {
     turn = "O";

    } else {
     turn = "X";
    }

    printBoard();
    winner = checkWinner();

   } else {

    System.out.println("Slot already taken; re-enter slot number:");
    continue;
   }

  }

  //game will end with a draw
  if (winner.equalsIgnoreCase("draw")) {
   System.out.println("It's a draw! Thanks for playing.");

  //game will end when there is a winner
  } else {
   System.out.println("Congratulations! " + winner + "'s have won! Thanks for playing.");
  }

}

//all of the options available for when a player aligns 3 X's or O's
static String checkWinner() {
  for (int a = 0; a < 8; a++) {
   String line = null;

   switch (a) {
   case 0:

    line = board[0] + board[1] + board[2];

    break;

   case 1:

    line = board[3] + board[4] + board[5];

    break;

   case 2:

    line = board[6] + board[7] + board[8];

    break;

   case 3:

    line = board[0] + board[3] + board[6];

    break;

   case 4:

    line = board[1] + board[4] + board[7];

    break;

   case 5:

    line = board[2] + board[5] + board[8];

    break;

   case 6:

    line = board[0] + board[4] + board[8];

    break;

   case 7:

    line = board[2] + board[4] + board[6];

    break;
   }

   if (line.equals("XXX")) {
    return "X";

   } else if (line.equals("OOO")) {
    return "O";
   }

  }

  for (int a = 0; a < 9; a++) {
   if (Arrays.asList(board).contains(String.valueOf(a+1))) {
    break;
   }
   else if (a == 8) return "draw";
  }

  System.out.println(turn + "'s turn; enter a slot number to place " + turn + " in:");
  return null;
}

//making the board
static void printBoard() {
  System.out.println("/---|---|---\\");

  System.out.println("| " + board[0] + " | " + board[1] + " | " + board[2] + " |");

  System.out.println("|-----------|");

  System.out.println("| " + board[3] + " | " + board[4] + " | " + board[5] + " |");

  System.out.println("|-----------|");

  System.out.println("| " + board[6] + " | " + board[7] + " | " + board[8] + " |");

  System.out.println("/---|---|---\\");
}

static void populateEmptyBoard() {
  for (int a = 0; a < 9; a++) {
   board[a] = String.valueOf(a+1);
  }

}

public String getName() {
  return "A game of Tic-Tac-Toe";
  }
}