Map 按Key排序 和 按Value排序

https://www.cnblogs.com/binz/p/6671917.html

一、根据value排序

通用方法

public class MapUtil {
    public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map) {
        List<Map.Entry<K, V>> list = new LinkedList<Map.Entry<K, V>>(map.entrySet());
        Collections.sort(list, new Comparator<Map.Entry<K, V>>() {
            public int compare(Map.Entry<K, V> o1, Map.Entry<K, V> o2) {
                return (o1.getValue()).compareTo(o2.getValue());
            }
        });
 
        Map<K, V> result = new LinkedHashMap<K, V>();
        for (Map.Entry<K, V> entry : list) {
            result.put(entry.getKey(), entry.getValue());
        }
        return result;
    }
}

java7

public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map) {
        List<Map.Entry<K, V>> list = new LinkedList<>(map.entrySet());
        Collections.sort(list, new Comparator<Map.Entry<K, V>>() {
            @Override
            public int compare(Map.Entry<K, V> o1, Map.Entry<K, V> o2) {
                return (o1.getValue()).compareTo(o2.getValue());
            }
        });
 
        Map<K, V> result = new LinkedHashMap<>();
        for (Map.Entry<K, V> entry : list) {
            result.put(entry.getKey(), entry.getValue());
        }
        return result;
}

    public static Map<String, String> sortMapByValue(Map<String, String> oriMap) {
        if (oriMap == null || oriMap.isEmpty()) {
            return null;
        }
        Map<String, String> sortedMap = new LinkedHashMap<String, String>();
        List<Map.Entry<String, String>> entryList = new ArrayList<Map.Entry<String, String>>(
                oriMap.entrySet());
        Collections.sort(entryList, new Comparator<Map.Entry<String, String>> {
            @Override
            public int compare(Entry<String, String> me1, Entry<String, String> me2) {
                return me1.getValue().compareTo(me2.getValue());
            }
        });

        Iterator<Map.Entry<String, String>> iter = entryList.iterator();
        Map.Entry<String, String> tmpEntry = null;
        while (iter.hasNext()) {
            tmpEntry = iter.next();
            sortedMap.put(tmpEntry.getKey(), tmpEntry.getValue());
        }
        return sortedMap;
    }

java8

public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue(Map<K, V> map) {
       Map<K, V> result = new LinkedHashMap<>();
       Stream<Entry<K, V>> st = map.entrySet().stream();
 
       st.sorted(Comparator.comparing(e -> e.getValue())).forEach(e -> result.put(e.getKey(), e.getValue()));
 
       return result;
   }

二、根据key排序

    public static Map<String, String> sortMapByKey(Map<String, String> map) {
        if (map == null || map.isEmpty()) {
            return null;
        }
        Map<String, String> sortMap = 
                new TreeMap<>(Comparator.naturalOrder());
        //      new TreeMap<>((str1, str2) -> str1.compareTo(str2));
        sortMap.putAll(map);
        return sortMap;
    }