public static void main(String[] args) {

    ArrayList<String> string;

    string = new ArrayList<>(Arrays.asList("Mah", "Bob", "mah", "bat", "MAh", "BOb"));

    Map<String, Integer> wordMap = new HashMap<String, Integer>();

​

    for (String st : string) {

        String input = st.toUpperCase();

        if (wordMap.get(input) != null) {

            Integer count = wordMap.get(input) + 1;

            wordMap.put(input, count);

        } else {

            wordMap.put(input, 1);

        }

    }

    System.out.println(wordMap);

    Object maxEntry = Collections.max(wordMap.entrySet(), Map.Entry.comparingByValue()).getKey();

    System.out.println("maxEntry = " + maxEntry);

}

​