Map 排序

详见：http://blog.yemou.net/article/query/info/tytfjhfascvhzxcytp42

[size=12px;][size=12px;][size=12px;]Map的排序常分为两种情况，1、按[/size]key[size=12px;]值排序；2、按value排序[/size][/size][/size]

[size=12px; font-family: 宋体;]    1.[size=12px; font-family: 宋体;]我们先讨论按[/size]key[size=12px; font-family: 宋体;]值进行排序[/size]
[size=12px; font-family: 宋体;]我们先看一下这个[/size]Sorter[size=12px; font-family: 宋体;]类：[/size][/size]

[size=12px; font-family: 宋体;]    public static Map sort(Map map) {
         Map mapVK = new TreeMap(
             new Comparator() {
                 public int compare(Object obj1, Object obj2) {
                     String v1 = (String)obj1;
                     String v2 = (String)obj2;
                     int s = v2.compareTo(v1);
                     return s;
                 }
             }
         );[/size]
[size=12px; font-family: 宋体;]        Set col = map.keySet();
         Iterator iter = col.iterator();
         while (iter.hasNext()) {
             String key = (String) iter.next();
             Integer value = (Integer) map.get(key);
             mapVK.put(key, value);
         }
         return mapVK;
     }
    
}[/size]

public class SortHashMap {

[size=12px; font-family: 宋体;]    }[/size]
[size=12px; font-family: 宋体;]    public static void main(String[] args) {
         Map maps = new HashMap();
         maps.put("boy",;
         maps.put("cat", 7);
         maps.put("dog", 1);
         maps.put("apple", 5);
         //排序前的输出[/size]
         Set set = maps.entrySet();
         Iterator i = set.iterator();
         while(i.hasNext()){
             Map.Entry entry1=(Map.Entry)i.next();
             System.out.println(entry1.getKey() + "-------->" + entry1.getValue());
         }
[size=12px; font-family: 宋体;]        System.out.println("----------------");
          //排序后的输出[/size]
         Map sortMaps = Sorter.sort(maps);
         Set sortSet = sortMaps.entrySet();
         Iterator ii = sortSet.iterator();
         while(ii.hasNext()){
             Map.Entry entry1=(Map.Entry)ii.next();
             System.out.println(entry1.getKey() + "-------->" + entry1.getValue());
         }
        
     }
}

cat-------->7
apple-------->5
dog-------->1
boy-------->8

dog-------->1
cat-------->7
boy-------->8
apple-------->5
经过排序后的Map有序了，是按照字母的逆序排列的。

还是上面的那个例子，我们想要按照各类对象的数量打印出类别的名称。
我们再来修改一下这个SortHashMap类：

[size=12px; font-family: 宋体;]    public SortHashMap() {[/size]

[size=12px; font-family: 宋体;]    public static void main(String[] args) {
         Map maps = new HashMap();
         maps.put("boy",;
         maps.put("cat", 7);
         maps.put("dog", 1);
         maps.put("apple", 5);
         //排序前的输出[/size]
         Set set = maps.entrySet();
         Iterator i = set.iterator();
         while(i.hasNext()){
             Map.Entry entry1=(Map.Entry)i.next();
             System.out.println(entry1.getKey() + "-------->" + entry1.getValue());
         }
[size=12px; font-family: 宋体;]        System.out.println("----------------");
         //排序后的输出[/size]
      List> info = new ArrayList>(maps.entrySet());
         Collections.sort(info, new Comparator>() {
             public int compare(Map.Entry obj1, Map.Entry obj2) {
                 return obj2.getValue() - obj1.getValue();
             }
         });
[size=12px; font-family: 宋体;]        for (int j = 0; j" + info.get(j).getValue());
         }
     }
}[/size]

cat-------->7
apple-------->5
dog-------->1
boy-------->8

boy------->8
cat------->7
apple------->5
dog------->1