@Override public String toString ()
  {
    StringBuffer result = new StringBuffer (500);
    int i, j;
    String cols = "     A   B   C   D   E\n";
    String space= "   +---+---+---+---+---+\n";
    result.append(cols);
    for (i=1; i<=5; i++) {
      result.append(space);
      result.append(" "+i+" ");
      for (j=1; j<=5; j++) { 
        result.append("| ");
        switch (board[i][j]) {
          case BLACK:   result.append("x "); break;
          case NEUTRON: result.append("* "); break;
          case WHITE:   result.append("o "); break;
          case EMPTY:   result.append("  "); break;
	  default:
            //This should never happen
            assert(false);
        }
      }
      result.append("| "+i);
      if (i==1) result.append(" <- Black's back row");
      if (i==5) result.append(" <- White's back row");
      result.append("\n");
    }
    result.append(space);
    result.append(cols);
    return result.toString ();
  }