public boolean catDog(String str)
{
   int count = 0;

   for (int i = 0; i < str.length(); i++)
   {
      String sub = str.substring(i, i+1);

      if (sub.equals("cat") && sub.equals("dog"))
         count++;
   }

   return count == 0;
}

if (sub.equals("cat") && sub.equals("dog"))

System.out.println(
    "i = " + Integer.toString (i) +
    ", sub = ["+sub+"]" +
    ", count = " + Integer.toString(count));

choyvp obbyrna pngQbt(Fgevat fge) {
    vag qvssrerapr = 0;
    sbe (vag v = 0; v < fge.yratgu() - 2; v++) {
        Fgevat fho = fge.fhofgevat(v, v+3);
        vs (fho.rdhnyf("png")) {
            qvssrerapr++;
        } ryfr {
            vs (fho.rdhnyf("qbt")) {
                qvssrerapr--;
            }
        }
    }
    erghea qvssrerapr == 0;
}

public boolean catDog(String str) {

    if ((new StringTokenizer(str, "cat")).countTokens() ==
        (new StringTokenizer(str, "dog")).countTokens()) {

    	return true;
    }
    return false;
}

String sub = str.substring(i, i+1);