Something

    public String toString() {
        int k=8;
        String str = "";
        
        for(int i=0;i<15;i++) {
            for(int h=0;h<(18-k/2);h++) {
                str += " ";
            }
            
            for(int j=0;j<k;j++) {
                if (j==k/2) 
                    str += " ";
                if (chart[i][j].getName().equals(""))
                    str += "x";
                else str += "o";
            }
            str += "\n";
            k+=2;
        }
        return str;
    }