package com.cute.test;

import java.util.Comparator;
import java.util.Map;
import java.util.TreeMap;

public class SortMapTest {

  public static void main(String[] args) {
    Map tmap = new TreeMap();
    tmap.put("abc", "2");
    tmap.put("ace", "3");
    tmap.put("cef", "2");
    tmap.put("Weight", "6");
    tmap.put("BLue", "6");
    tmap.put("BLUe", "6");

    //对map利用key排序
    Map resMap = sortMapByKey(tmap);

    for (Map.Entry entry : resMap.entrySet()) {
      System.out.println(entry.getKey() + " " + entry.getValue());
    }
  }

  /**
   * 让 Map按key进行排序
   */
  public static Map sortMapByKey(Map map) {
    if (map == null || map.isEmpty()) {
      return null;
    }
    Map sortMap = new TreeMap(new MapKeyComparator());
    sortMap.putAll(map);
    return sortMap;
  }
}

//实现一个比较器类

class MapKeyComparator implements Comparator {

  @Override
  public int compare(String s1, String s2) {
    return s1.compareTo(s2);  //从小到大排序
  }
}

输出结果：

BLUe 6

BLue 6

Weight 6

abc 2

ace 3

cef 2