这个在JAVA中怎么实现呀？ 统计Please help me open the door这个字符串

这个在JAVA中怎么实现呀？ 统计Please help me open the door这个字符串中每个单词出现的次数，然后将所有的换成a

    public static HashMap<Character, Integer> simple(String value) {
        value = value.replace(" ", "");
        char[] chars = value.toCharArray();
        HashMap<Character, Integer> map = new HashMap<>();
        for (char val : chars) {
            Integer integer = map.get(val);
            if (integer == null) {
                map.put(val, 1);
            }else {
                map.put(val, integer + 1);
            }
        }
        return map;
    }