Passing a boolean result into another methods if statement. (tic-tac-toe game)

public boolean isWinner(char player)
{
        if (board[0] == player && board[1] == player && board[2] == player ||
            board[3] == player && board[4] == player && board[5] == player ||
            board[6] == player && board[7] == player && board[8] == player ||
            board[0] == player && board[3] == player && board[6] == player ||
            board[1] == player && board[4] == player && board[7] == player ||
            board[2] == player && board[5] == player && board[8] == player )
            return 1;

  return 0;  
}
/* check to see if the player x is the winner or
   the player y is the winner or the cat is the winner 
    or the game is not over yet  and then display the result
     you need to write conditional statments*/
public void displayResults()
{
  if (isWinner = true)
     System.out.print("CONGRATUTIONS " + player + " YOU WON!");
}

Hey I was wondering if anyone could help me on how to pass the the "isWinner" result into "displayResults" if statement. This is for a tic-tac-toe game that we got assigned if this is one of the parts I need help on.