java中map的排序问题

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java中Map排序问题

按key排序

public class MapSortDemo {    public static void main(String[] args) {        Map<String, String> map = new TreeMap<String, String>();        map.put("KFC", "kfc");        map.put("WNBA", "wnba");        map.put("NBA", "nba");        map.put("CBA", "cba");        Map<String, String> resultMap = sortMapByKey(map);             for (Map.Entry<String, String> entry : resultMap.entrySet()) {            System.out.println(entry.getKey() + " " + entry.getValue());        }    }    public static Map<String, String> sortMapByKey(Map<String, String> map) {        if (map == null || map.isEmpty()) {            return null;        }        Map<String, String> sortMap = new TreeMap<String, String>(                new MapKeyComparator());        sortMap.putAll(map);        return sortMap;    }}class MapKeyComparator implements Comparator<String>{    @Override    public int compare(String str1, String str2) {        return str1.compareTo(str2);    }}

按value排序

public class Main {    public static void main(String[] args) {        Scanner sc = new Scanner(System.in);        while(sc.hasNext()){            Map<Character, Integer> map = new LinkedHashMap<>();            String sentence = sc.nextLine();            char[] arr = sentence.toCharArray();            for(int i=0;i<arr.length;i++){                if((arr[i] >= 'A' && arr[i] <= 'Z') ||                        (arr[i] >='a' && arr[i] <= 'z')||                        arr[i] >= '1' && arr[i] <= '9' ||                        arr[i]==' '){                    if(map.get(arr[i]) != null){                        map.put(arr[i], map.get(arr[i])+1);                    }else{                        map.put(arr[i], 1);                    }                }            }            // 转化为list            List<Map.Entry<Character, Integer>> entryList = new ArrayList<Map.Entry<Character, Integer>>(                    map.entrySet());            //  public static <T> void sort(List<T> list, Comparator<? super T> c)             Collections.sort(entryList, new MapValueComparator());            for (Map.Entry<Character, Integer> cc : entryList) {                System.out.print(cc.getKey());            }        }    }    private static class MapValueComparator implements Comparator<Map.Entry<Character, Integer>>{        @Override        public int compare(Map.Entry<Character, Integer> o1, Map.Entry<Character, Integer> o2) {            if(o1.getValue() < o2.getValue())                return 1;            else if(o1.getValue() == o2.getValue())                return o1.getKey()-(o2.getKey());            else                return -1;        }    }}

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