JAVA中对list map根据map某个key值进行排序

package test;
 
import java.util.ArrayList;
 
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
public class java_ListMapSort {
    public static void main(String[] args) {
        // TODO Auto-generated method stub 
        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
        Map<String, Object> map1 = new HashMap<String, Object>();
        map1.put("name", "p");
        map1.put("age", "5");
        Map<String, Object> map2 = new HashMap<String, Object>();
        map2.put("name", "h");
        map2.put("age", "12");
        Map<String, Object> map3 = new HashMap<String, Object>();
        map3.put("name", "f");
        map3.put("age", "31");
        list.add(map1);
        list.add(map3);
        list.add(map2);
        //排序前 
        for (Map<String, Object> map : list) {
            System.out.println(map.get("age"));
        }
        Collections.sort(list, new Comparator<Map<String, Object>>() {
            public int compare(Map<String, Object> o1, Map<String, Object> o2) {
                Integer age1= Integer.valueOf(o1.get("age").toString()) ;//age1是从你list里面拿出来的第一个 age
                Integer age2= Integer.valueOf(o2.get("age").toString()) ; //age1是从你list里面拿出来的第二个age
                return age1.compareTo(age2);   //return age2.compareTo(age1);为降序
            }
        });
        //排序后 
        System.out.println("-------------------");
        for (Map<String, Object> map : list) {
            System.out.println(map.get("age"));
        }
    }
}