public synchronized void printInvisibleFields()
    {
        for (int k = 0; k < SIZE; k++)
        {
            for (int l = 0; l < SIZE; l++)
            {
                if (fField[k][l] == VALUE_SHIP)
                {
                    System.out.print("S ");
                }
                if (fField[k][l] == VALUE_FREE)
                {
                	System.out.print("~ ");
                }
                if (fField[k][l] == VALUE_SHIP_HIT)
                {
                	System.out.print("X ");
                }
                if (fField[k][l] == VALUE_FREE_HIT)
                {
                	System.out.print("0 ");
                }
            }
            System.out.println(" ");
        }
        System.out.println(" ");
    }