String test = "ZZZAABCDA";
        HashMap<Character, Integer> myMap = new HashMap<>();
        for (int index = 0; index < test.length(); index++) { // each char..
            char c = test.charAt(index);
            if (myMap.containsKey(c)) // already there
            {
                myMap.put(c, myMap.get(c) + 1); // add 1
            } else {
                myMap.put(c, 1); // else add with count 1
            }
        }
        for (char c : myMap.keySet()) // show result
        {
            System.out.println(c + " " + myMap.get(c));
        }
    }