catDog string problem at Codingbat.com

Question

Could anyone check my solution?

I want to return true if the string "cat" and "dog" appear the same number of times in the given string. There are various strings with different numbers of "cat" and "dog".

public boolean catDog(String str) 
{  
  int catAnswer = 0;
  int dogAnswer = 0;
  int cat_Count = 0;
  int dog_Count = 0;

  for (int i=0; i< str.length()-1; i++) 
  {
    String sub = str.substring(i, i+2);


    if ((sub.equals("cat")))  cat_Count++;
    if ((sub.equals("dog")))  dog_Count++;
    catAnswer = cat_Count; 
    dogAnswer = dog_Count;

  } //end for

  if(dogAnswer == catAnswer ) {return true;}
  // else
  return (dogAnswer != catAnswer);
}

UPDATE:

1. If i use i + 3 i get an error code Exception:java.lang.StringIndexOutOfBoundsException: String index out of range: 7 (line number:10) - hence i use i + 2 (no errors are reported with it

2. Changing to i < str.length() - 4 gives a blanket response of true despite some of the test strings containing an unequal number of "cat" & "dog " tokens

The crux of the problem is that the response is either all true or all false when there is variable numbers of "cat" & "dog" in the various strings

the output from the code can be seen at http://codingbat.com/prob/p111624 - catDog string problem

Please try in cutting and pasting my code to see the output - this will explain more graphically than i could say

Answer 1

1. if i use i + 3 i get an error code Exception:java.lang.StringIndexOutOfBoundsException: String index out of range: 7 (line number:10) - hence i use i + 2 (no errors are reported with it 2.changing to i < str.length() - 4 gives a blanket response of true despite some of the test strings containing an unequal number of "cat" & "dog " tokens

The crux of the problem is that the response is either all true or all false despite there being a variable numbers of "cat" & "dog" tokens in the various strings

the output from the code can be seen at http://codingbat.com/prob/p111624 - catDog string problem

Please try in cutting and pasting my code to see the output - this will explain more graphically than i could say

Answer 2

A solution with less duplication would be to write a function that counts occurrences of a substring within a string, then call that function with the string and "cat", and with the string and "dog", and return whether the two counts agree.

Answer 3

int count(String needle, String haystack) {
  return haystack.split(needle, -1).length - 1;
}

public boolean catDog(String str) {
  return count("dog", str) == count("cat", str);
}

Here's an "All Correct" solution that uses split. The -1 is used to preserve trailing empty strings.