Java中HashMap排序

注：

    转载于 http://www.cnblogs.com/xingyun/archive/2012/12/09/2809962.html

package com.holdobject;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

public class HashMapSort {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<String, Integer>();
        map.put("d", 3);
        map.put("c", 1);
        map.put("b", 1);
        map.put("a", 2);

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

        System.out.println("Before Sort....");
        for (int i = 0; i < infoIds.size(); i++) {
            System.out.println(infoIds.get(i).toString());
        }

        System.out.println("\n\nAfter Sort(Key)....");

        Collections.sort(infoIds, new Comparator<Map.Entry<String, Integer>>() {
            public int compare(Entry<String, Integer> o1,
                    Entry<String, Integer> o2) {
                return o1.getKey().toString().compareTo(o2.getKey());
            }
        });

        for (int i = 0; i < infoIds.size(); i++) {
            System.out.println(infoIds.get(i).toString());
        }

        System.out.println("\n\nAfter Sort(Value)....");

        Collections.sort(infoIds, new Comparator<Map.Entry<String, Integer>>() {
            public int compare(Entry<String, Integer> o1,
                    Entry<String, Integer> o2) {
                return o1.getValue() - (o2.getValue());
            }
        });

        for (int i = 0; i < infoIds.size(); i++) {
            System.out.println(infoIds.get(i).toString());
        }
    }
}

注：

        以上实现，调用了Collection.sort接口，其中sort函数的参数是List<T>泛型

Map.Entry<String,Double> 为HashMap中的键值对

 

参考资料：

         http://blog.csdn.net/zxy_snow/article/details/7232035