java - What is wrong with my TicTacToe code and how do you check already taken spots? -

i have edited question. feel close reason output of code prints 'x' or 'o' above board. can't pinpoint why doing , how check if spot taken , not allow spot overridden. have tried putting if(board[i][j]!= ' ') {s.o.p("not valid") }but not function correctly. maybe i'm not writing in wrong spot?

the last thing when want restart game winner declared. how game reset board?

i have been @ hours , appreciate help.

import java.util.scanner;  public class tictactoe { public static char[][] board = new char[3][3];  public static char player; public static void newgame() {     system.out.println("new game: x goes first.");     player = 'x'; }  public static void writeboard() {     //drawing game board     string line = "______";     system.out.println("");     //making seperate columns , rows     for(int i= 0;i<3; i++)     {         for(int j=0;j<3;j++)         system.out.print(board[i][j]+"|");         system.out.println("");         system.out.println(line);     } }  public static void getmove() {     scanner keyboard = new scanner(system.in);     int i, j;     if(player == 'x')     {         system.out.println("x's turn");         system.out.println("where want x placed?");         system.out.println("please enter row number , column number seperated space.");         = keyboard.nextint();         j = keyboard.nextint();             if(board[i][j] != ' ')                 system.out.println("that position taken");         system.out.println("you have entered row" + " " + + " "+ "and column" + " " + j);         system.out.println("thank selection.");         system.out.print(board[i][j]='x');         player = 'o';      }     else if(player == 'o')     {         system.out.println("o's turn");         system.out.println("where want o placed?");         system.out.println("please enter row number , column number seperated space.");         = keyboard.nextint();         j = keyboard.nextint();             if(board[i][j] != ' ')                 {                     system.out.println("that position taken");                 }         system.out.println("you have entered row"+" " + +" "+ "and column" +" " + j);         system.out.println("thank selection.");         system.out.println(board[i][j] = 'o');         player = 'x';      }  }   public static boolean winner() {     //check row     (int = 0; < 3; i++)     {         if (board[i][0] == board[i][1] && board[i][1] == board[i][2] && (board[i][0] == 'x'))         {             system.out.println("x winner");             return true;         }         else if (board[i][0] == board[i][1] && board[i][1] == board[i][2] &&(board[i][0]=='o'))         {             system.out.println("o winner");             return true;         }          //check column         else if (board[0][i] == board[1][i] && board[1][i] == board[2][i] && (board[0][i] =='x'))         {             system.out.println("x winner");             return true;         }         else if (board[0][i] == board[1][i] && board[1][i] == board[2][i] && (board[0][i]=='o'))         {             system.out.println("o winner");             return true;         }     }          //check diagnols left         if (board[0][0] == board[1][1] && board[1][1] == board[2][2] && (board[0][0]=='o'))         {             system.out.println("o winner!");             return true;         }         else if (board[0][0] == board[1][1] && board[1][1] == board[2][2] && (board[0][0] == 'x'))         {             system.out.println("x winner!");             return true;         }         //checks diagnols right         else if (board[0][2] == board[1][1] && board[1][1] == board[2][0] && (board[0][2]=='o'))         {             system.out.println("o winner!");             return true;         }         else if (board[0][2] == board[1][1] && board[1][1] == board[2][0] && (board[0][2]=='x'))         {             system.out.println("x winner!");             return true;         }         else         {             return false;         } }   public static boolean tie() {     //if there no winner(a tie)     for(int i=0;i<3;i++)     {         for(int j=0; j<3;j++)         {             if(board[i][j]==' ')             {                 system.out.println("it's tie!");                 return false;             }         }     }     return true; }  }        import java.util.scanner;  public class tictactoedemo { public static char[][] board = new char[3][3];  public static void main(string[] args) {     scanner keyboard = new scanner(system.in);      int i, j;     string answer;      do{          tictactoe.newgame();          while(!tictactoe.winner())         {             tictactoe.writeboard();             tictactoe.getmove();             tictactoe.tie();         }          system.out.println("would rematch?");         system.out.println("enter yes or no");         answer = keyboard.next();        } while(answer.equalsignorecase("yes"));     //do-while loop keep game going if wanted } } 

tictactoe class

newgame() missing return statement, add void

player not initialized, make global variable with:

private static char player; public static void newgame() {   system.out.println("new game: x goes first.");   player = 'x'; } 

do refactoring of winner method, complex. maybe separate conditions separate methods easier readability. can find lots of examples on how should done.

fix error handling (i entered "22 33" , got arrayindexoutofboundsexception, "a b" , got inputmismatchexception), need prevent this.

tictactoedemo class

board never used, , j also.

why do/while? can done while loop...

this few fixes made running need address other issues.

what ide using development? should report errors , give explanation of it.