Check if field is taken Tic Tac Toe java

Currently i am coding a simple tic tac toe code in java. Everything works fine but i have a problem.

int[] board = new int[9];
        for(int i = 0; i < board.length; i++){
            board[i] = 7;
        }

This is my board.It has 9 fields.

if(zug >= 9 || zug < 0){

                System.out.println("Dieses Feld gibt es nicht! Versuche es erneut!");
                zug1class(player, playerone1, playertwo2, board2,zug1check2 );
            }
            else if (zug < 9 || zug > 0){


                check = zug;
                System.out.println(check);
                meinBoard[zug] = 0;
            }

And this is my statement for setting a fied. But i want to implement that the code checks with the if statement if the field is taken. I tried it with this:

int[] fieldchecker= new int[9];
for(int i = 0; i < board.length; i++){
            board[i] = -1;
        }

And then after choosing a field:

fieldchecker[zug] = zug;

And then it checks in the if statement:

if(zug == fieldchecker[zug]{

   //Do something

}

But this doesnt work for me. :/ I hope you can help me :D

Marvin