java的Map排序（根据key或者value）

转载来源:https://www.cnblogs.com/ltb6w/p/7862251.html

一.key排序

(T o1,To2)方法即可实现排序，如下：

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)); 

        } 

    } 

}

d:aaaaa 

c:bbbbb 

b:ccccc 

a:ddddd

二.value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());  

          }  

    } 

}

d:aaaaa 

c:bbbbb 

b:ccccc 

a:ddddd

文章来源: java的Map排序（根据key或者value）