public void add(char[] w, int wLen)
{  if (i+wLen >= b.length)
   {  char[] new_b = new char[i+wLen+INC];
      for (int c = 0; c < i; c++) new_b[c] = b[c];
      b = new_b;
   }
   for (int c = 0; c < wLen; c++) b[i++] = w[c];
}