根据map中的key或者value值进行排序

1.根据key值进行排序

import java.util.Comparator;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

import java.util.TreeMap;

public class TreeMapTest {

public static void main(String[] args) {

Map<String, String> map = new TreeMap<String, String>(

new Comparator<String>() {

public int compare(String obj1, String obj2) {

// 降序排序

return obj2.compareTo(obj1);

}

});

map.put("b", "ccccc");

map.put("d", "aaaaa");

map.put("c", "bbbbb");

map.put("a", "ddddd");

        Set<String> keySet = map.keySet();

        Iterator<String> iter = keySet.iterator();

        while (iter.hasNext()) {

            String key = iter.next();

            System.out.println(key + ":" + map.get(key));

        }

    }

}

运行结果：

d:aaaaa

c:bbbbb

b:ccccc

a:ddddd

2.对value进行排序

import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

import java.util.List;

import java.util.Map;

import java.util.Map.Entry;

import java.util.TreeMap;

public class TreeMapTest {

public static void main(String[] args) {

        Map<String, String> map = new TreeMap<String, String>();

map.put("a", "ddddd");

map.put("c", "bbbbb");

map.put("d", "aaaaa");

map.put("b", "ccccc");

        //这里将map.entrySet()转换成list

        List<Map.Entry<String,String>> list = new ArrayList<Map.Entry<String,String>>(map.entrySet());

        //然后通过比较器来实现排序

        Collections.sort(list,new Comparator<Map.Entry<String,String>>() {

            //升序排序

            public int compare(Entry<String, String> o1,

                    Entry<String, String> o2) {

                return o1.getValue().compareTo(o2.getValue());

            }

        });

        for(Map.Entry<String,String> mapping:list){

               System.out.println(mapping.getKey()+":"+mapping.getValue());

          }

    }

}

运行结果如下：

d:aaaaa

c:bbbbb

b:ccccc

a:ddddd