Using recursion to find a character in a string

Question

I am trying to find the first occurrence of a letter in a string. For example, p in apple should return 1. Here is what I have:

// Returns the index of the          


        

Answer 1

Well if we must use recursion then try this:

class RecursiveFirstIndexOf {

public static void main(String[] args) {
    System.out.println(indexOf('p', "apple", 0));
}

static int indexOf(char c, String str, int currentIdx) {

    if (str == null || str.trim().isEmpty()) {
        return -1;
    }

    return str.charAt(0) == c ? currentIdx : indexOf(c, str.substring(1), ++currentIdx);

}}