The countSubstring function will take two strings as parameters and will return an integer that is the count of how many times the substring (the second parameter) appears in the first string without overlapping with itself. This method will be case insensitive.

For example:

countSubstring(catwoman loves cats, cat) would return 2

countSubstring(aaa nice, aa) would return 1 because aa only appears once without overlapping itself.

public static int countSubstring(String s, String x) {

if (s.length() == 0 || x.length() == 0)

return 1;

if (s.length() == 1 || x.length() == 1){

if (s.substring(0,1).equals(x.substring(0,1))){

s.replaceFirst((x), " ");

return 1 + countSubstring(s.substring(1), x);

}

else {

return 0 + countSubstring(s.substring(1), x);

}

}

return countSubstring(s.substring(0,1), x) + countSubstring(s.substring(1), x);

}

public class Main {

public static void main(String[] args) {

System.out.println(Recursion.countSubstring("catwoman loves cats","cat"));

System.out.println(Recursion.countSubstring("aaa nice","aa"));

}

}