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());
}