排序map

1、根据map的值，升序排序

 Map<String, Integer> map = new TreeMap<String, Integer>();
 map.put("d", 1);
 map.put("b", 2);
 map.put("a", 3);
 map.put("c", 4);

 // 这里将map.entrySet()转换成list
 List<Map.Entry<String, Integer>> list = new ArrayList<Map.Entry<String, Integer>>(map.entrySet());
 // 然后通过比较器来实现排序
 Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() {
     // 升序排序
     public int compare(Entry<String, Integer> o1, Entry<String, Integer> o2) {
         return o1.getValue().compareTo(o2.getValue());
     }

 });
 for (Map.Entry<String, Integer> mapping : list) {
     System.out.println(mapping.getKey() + ":" + mapping.getValue());
 }