What's more efficient for counting, Arrays or Hashmap(or Set)

Assume we're asked to count and print the occurrences of each character in a given String. For simplicity, the string has just lowercase letters. I wrote these 2 functions and I want to know which one is more efficient/preferable in Java.

Function 1:

private void countAndPrintArray1(String str){
        int[] a = new int[26];
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            int index = c - 'a';
            a[index] = a[index] + 1;
        }

        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            int freq = a[c -'a'];
            System.out.println(c+" -> "+ freq);
        }
    }

Function 2:

    private void countAndPrintArray2(String str){
        Map<Character, Integer> map = new HashMap<>();

        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            int freq = map.getOrDefault(c, 0) + 1;
            map.put(c, freq);
        }

        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            int freq = map.get(c);
            System.out.println(c+" -> "+ freq);
        }
    }