java中，map集合排序实例

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1.实体类

package test;
/**
* 学生实体类
* @author xf
*
*/
public class Student {
   private String name;
   private int avg;
   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }
   public int getAvg() {
       return avg;
   }
   public void setAvg(int avg) {
       this.avg = avg;
   }
}

2.map集合排序实现类

package test;

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

/**
* map集合排序
* @author xf
*
*/
public class MapKeyComparator implements Comparator<String> {
   @Override
   public int compare(String str1, String str2) {
       int num=str1.compareTo(str2);
       if(num>0){ //降序
           return -1;
       }else{
           return 1;
       }
       /*if(num>0){ //升序
           return 1;
       }else{
           return -1;
       }*/
   }

    /**
     * 使用 Map按key进行排序
     * @param map
     * @return
     */
    public static Map<String, Student> sortMapByKeyStu(Map<String, Student> map) {
        if (map == null || map.isEmpty()) {
            return null;
        }
        Map<String, Student> sortMap = new TreeMap<String, Student>(
                new MapKeyComparator());

        sortMap.putAll(map);

        return sortMap;
    }
}

3.测试类

package test;

import java.util.HashMap;
import java.util.Map;

public class Test_sdgd {
   public static void main(String[] args) {
       try {
           Map<String, Student> map = new HashMap<String, Student>();
           map.put("2009", new Student());
           map.put("2016", new Student());
           map.put("2005", new Student());
           map.put("2001", new Student());
           map.put("2014", new Student());
           map.put("2011", new Student());
           map.put("2010", new Student());
           map.put("2012", new Student());
           map=MapKeyComparator.sortMapByKeyStu(map);
           for (Map.Entry<String, Student> entry : map.entrySet()) {
               System.out.println(entry.getKey());
           }
       } catch (Exception e) {
           e.printStackTrace();
       }
   }
}

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