NullPointerException while calling function that print values of full multidimensional array

Question

guys I'm trying to build Tic-Tac-Toe from scratch by using java, I'm aware it's not may be perfect but I will try anyway! I wrote a function that should printing the board when I'm calling it but it's gives me NullPointerException idk why tbh

import java.io.*;
import java.util.*;
class Task_3{
    static char[][] board;
    static void checkWinner(){
        String v=null;
        for(int p=0;p<8;p++){
            switch(p){
                case 0:
                    v=String.valueOf(board[0][0]+board[0][1]+board[0][2]);
                    break;
                case 1:
                    v=String.valueOf(board[1][0]+board[1][1]+board[1][2]);
                    break;
                case 2:
                    v=String.valueOf(board[2][0]+board[2][1]+board[2][2]);
                    break;
                case 3:
                    v=String.valueOf(board[0][0]+board[1][0]+board[2][0]);
                    break;
                case 4:
                    v=String.valueOf(board[0][1]+board[1][1]+board[2][1]);
                    break;
                case 5:
                    v=String.valueOf(board[0][2]+board[1][2]+board[2][2]);
                    break;
                case 6:
                    v=String.valueOf(board[0][0]+board[1][1]+board[2][2]);
                    break;
                case 7:
                    v=String.valueOf(board[0][2]+board[1][1]+board[2][0]);
                    break;
            }
            if (v.equals("XXX")){
                System.out.println("X is The Winner!");
            }else if(v.equals("OOO")){
                System.out.println("O is The Winner!");
            }else{
                System.out.println("Tie");
            }
        }
    }
    static void printBoard()
    {
        System.out.println("|---|---|---|");
        System.out.println("| " + board[0][0] + " | "
                           + board[0][1] + " | " + board[0][2]
                           + " |");
        System.out.println("|-----------|");
        System.out.println("| " + board[1][0] + " | "
                           + board[1][1] + " | " + board[1][2]
                           + " |");
        System.out.println("|-----------|");
        System.out.println("| " + board[2][0] + " | "
                           + board[2][1] + " | " + board[2][2]
                           + " |");
        System.out.println("|---|---|---|");
    }
    public static void main (String[] args) {
    int pos=0, xoro=1;
    Scanner sc = new Scanner(System.in);
    char[][] board = new char[3][3];
    board[0][0]=1;
    board[0][1]=2;
    board[0][2]=3;
    board[1][0]=4;
    board[1][1]=5;
    board[1][2]=6;
    board[2][0]=7;
    board[2][1]=8;
    board[2][2]=9;
    printBoard();
    pos = sc.nextInt();
    switch(pos){
        case 1:
            if (xoro % 2 == 0)
                board[0][0]='O';
                else
                    board[0][0]='X';
                xoro++;
                for (int i = 0; i < 3; i++)
            for (int j = 0; j < 3; j++)
                System.out.println(board[i][j]);
            break;
        case 2:
            if (xoro % 2 == 0)
            board[0][1]='O';
                else
                    board[0][1]='X';
                xoro++;
            break;
        case 3:
            if (xoro % 2 == 0)
            board[0][2]='O';
                else
                    board[0][2]='X';
                xoro++;
            break;
        case 4:
            if (xoro % 2 == 0)
            board[1][0]='O';
                else
                    board[1][0]='X';
                xoro++;
            break;
        case 5:
            if (xoro % 2 == 0)
            board[1][1]='O';
                else
                    board[1][1]='X';
                xoro++;
            break;
        case 6:
            if (xoro % 2 == 0)
            board[1][2]='O';
                else
                    board[1][2]='X';
                xoro++;
            break;
        case 7:
            if (xoro % 2 == 0)
            board[2][0]='O';
                else
                    board[2][0]='X';
                xoro++;
            break;
        case 8:
            if (xoro % 2 == 0)
            board[2][1]='O';
                else
                    board[2][1]='X';
                xoro++;
            break;
        case 9:
            if (xoro % 2 == 0)
            board[2][2]='O';
                else
                    board[2][2]='X';
                xoro++;
            break;
    }
    }
}

and this is the error I got

|---|---|---|
Exception in thread "main" java.lang.NullPointerException
    at Task_3.printBoard(Task_3.java:46)
    at Task_3.main(Task_3.java:72)

Process completed.

tbh I don't know what seems what be the problem also I'm not that professional in java so sorry if it's was to basic. Thank you guys.. have a nice day.