刚刚学java不会，请大神帮忙解答

Question

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Answer 1

    public static void main(String[] args) {
        String str = "It's the first day of class, and the room is buzzing with excitement and expectation,curiosity and uncertainty";
        String[] strArrs = str.split(" ");
        HashMap<String, Integer> map = new HashMap<String, Integer>();
        for (int i = 0; i < strArrs.length; i++) {
            if (map.get(strArrs[i]) != null) {
                Integer integer = map.get(strArrs[i]);
                integer++;
                map.put(strArrs[i], integer);
            } else {
                map.put(strArrs[i], 1);
            }
        }

        int maxNum = 0;
        String maxValue = null;
        for (int i = 0; i < strArrs.length; i++) {
            int tmp = map.get(strArrs[i]);
            if(tmp > maxNum) {
                maxNum = tmp;
                maxValue = strArrs[i];
            }
        }

        System.out.println(maxValue + " : " + maxNum);
    }