1 集合

词频

输入：cat, dog, bird, dog, dog, cat
输出：
dog, 3
cat, 2
bird, 1

    public static void minRemoveToMakeValid(String s) {
        String[] split = s.split(", ");
        HashMap<String, Integer> map = new HashMap<>();
        for(String item : split){
            map.put(item, map.getOrDefault(item,0)+1);
        }
        for(Map.Entry entry : map.entrySet()){
            System.out.println(entry);
        }
    }
    public static void main(String[] args) {
        minRemoveToMakeValid("cat, dog, bird, dog, dog, cat");
        //用java8的stream 一行写
        String s = "cat, dog, bird, dog, dog, cat";
        String[] split = s.split(", ");
        TreeMap<String, Long> collect = Arrays.stream(split).collect(Collectors.groupingBy(Function.identity(), TreeMap::new, Collectors.counting()));
        collect.descendingMap().forEach((s1, aLong) -> System.out.println(s1 + ", " + aLong));
    }