import java.util.*; public class MapSortDemo { public static void main(String[] args) { Map<String, String> map = new HashMap<>(); map.put("1", "4"); map.put("3", "3"); map.put("2", "2"); map.put("4", "1"); //Map<String, String> resultMap = sortMapByKey(map); //按Key进行排序:1.treemap的性质 Map<String, String> resultMap = sortMapByKey2(map); //按key进行排序:2.list,自定义比较器(排序后需要LinkedHashMap保存) // Map<String, String> resultMap = sortMapByValue(map); //按Value进行排序:list,自定义比较器 for (Map.Entry<String, String> entry : resultMap.entrySet()) { System.out.println(entry.getKey() + " " + entry.getValue()); } } /** * 使用 TreeMap的性质按key进行排序 * @param map * @return */ public static Map<String, String> sortMapByKey(Map<String, String> map) { if (map == null || map.isEmpty()) { return null; } //TreeMap默认用key的自然排序,所以不用声明比较器也可以实现key排序,比较器可以自定义排序规则,比如倒序 //Map<String, String> sortMap = new TreeMap<String, String>(); //TreeMap构造方法可以有比较器参数~但是比较器只能是对key进行比较 Map<String, String> sortMap = new TreeMap<String, String>(new MapKeyComparator()); sortMap.putAll(map); return sortMap; } /** * 使用 list按key进行排序 * @param map * @return */ public static Map<String, String> sortMapByKey2(Map<String, String> map) { if (map == null || map.isEmpty()) { return null; } List<Map.Entry<String,String>> list = new ArrayList<>(map.entrySet()); Collections.sort(list,new MapKeyComparator2()); Map<String, String> sortMap = new LinkedHashMap<>(); Iterator<Map.Entry<String, String>> iterable = list.iterator(); while (iterable.hasNext()){ Map.Entry<String, String> tmpEntry = iterable.next(); sortMap.put(tmpEntry.getKey(),tmpEntry.getValue()); } return sortMap; } /** * 使用 List对Map按value进行排序 * @param oriMap * @return */ public static Map<String, String> sortMapByValue(Map<String, String> oriMap) { if (oriMap == null || oriMap.isEmpty()) { return null; } //一定是LinkedHashMap,因为LinkedHashMap保证put顺序和输出顺序一致! Map<String, String> sortedMap = new LinkedHashMap<>(); //map.entry把map的<key,value>当节点装进list,对list排序 List<Map.Entry<String, String>> entryList = new ArrayList<>(oriMap.entrySet()); Collections.sort(entryList, new MapValueComparator()); 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; } } class MapKeyComparator implements Comparator<String> { @Override public int compare(String str1, String str2) { return str2.compareTo(str1); } } class MapValueComparator implements Comparator<Map.Entry<String, String>> { @Override public int compare(Map.Entry<String, String> me1, Map.Entry<String, String> me2) { return me1.getValue().compareTo(me2.getValue()); } } class MapKeyComparator2 implements Comparator<Map.Entry<String, String>> { @Override public int compare(Map.Entry<String, String> me1, Map.Entry<String, String> me2) { return me1.getKey().compareTo(me2.getKey()); } }