/**
 * Counting the occurrences of a letter in a string
 * Lots of ways
 * @author gtowell
 * Created/Modified: Oct 21, 2021
 */
public class Counter {
    /*
    * This version is wrong
    */
    public int numOccur1(char ch, String str) {
        if (str == null || str.equals("")) {
            return 0;
        }
        int count = 0;
        if (str.charAt(0) == ch) {
            count++;
        }
        numOccur1(ch, str.substring(1));
        return count;
    }

    int acount = 0;

    /**
     * This version works but is bad
     * @param ch the char to look for
     * @param str the string to look in
     * @return count of the char
     */
    public int numOccur2(char ch, String str) {
        if (str == null || str.equals("")) {
            return 0;
        }
        if (str.charAt(0) == ch) {
            acount++;
        }
        numOccur2(ch, str.substring(1));
        return acount;
    }
    
    public int numOccur3(char ch, String str) {
        if (str == null || str.equals("")) {
            return 0;
        }
        int count = 0;
        if (str.charAt(0) == ch) {
            count = 1;
        }
        return count + numOccur3(ch, str.substring(1));
    }

    public int numOccur4(char ch, String str) {
        return numOccur4Util(ch, str, 0);
    }

    private int numOccur4Util(char ch, String str, int count) {
        if (str == null || str.equals("")) {
            return count;
        }
        if (str.charAt(0) == ch) {
            count++;
        }
        return numOccur4Util(ch, str.substring(1), count);
    }

    public int numOccur5(char ch, String str) {
        if (str == null || str.length()==0)
            return 0;
        return numOccur5Util(ch, str, 0, 0);
    }
    private int numOccur5Util(char ch, String str, int loc, int count) {
        if (loc >= str.length())
            return count;
        if (str.charAt(loc) == ch) { count++; }
        return numOccur5Util(ch, str, loc+1, count);
    }

    public int numOccur6(char ch, String str) {
        if (str == null || str.length()==0)
            return 0;
        return numOccur6Util(ch, str, 0);
    }
    private int numOccur6Util(char ch, String str, int loc) {
        if (loc >= str.length())
            return 0;
      return (str.charAt(loc)==ch ? 1 : 0) + numOccur6Util(ch, str, loc+1);
    }

    public static void main(String[] args) {
        Counter cc = new Counter();
        System.out.println(cc.numOccur5('a', "asdfgfdsawqaw"));
    }
}