2019-01-21_Java对list数据根据某个字段进行分组

package com.tech.ability.mycommonutils;

import com.alibaba.fastjson.JSONObject;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;

/**

• Created by kikop on 2019/1/21.
  */
  public class ListUtil {

  /**

  • 对list数据进行分组

  • @param srcList

  • @param comparator 条件比较器

  • @param <T>

  • @return 返回分组的结果
    */
    public static <T> List<List<T>> groupDataByCondition(List<T> srcList, Comparator<? super T> comparator) {

    List<List<T>> resultList = new ArrayList<>();

    for (int i = 0; i < srcList.size(); i++) {
    boolean isFindInCurrentGroups = false;

     //1.在现有组中查找
     for (int groupIndex = 0; groupIndex < resultList.size(); groupIndex++) {
         if (resultList.get(groupIndex).size() == 0 ||
                 comparator.compare(resultList.get(groupIndex).get(0), srcList.get(i)) == 0) {
             //没有直接添加或者与第j组第一个匹配
             resultList.get(groupIndex).add(srcList.get(i));
             isFindInCurrentGroups = true;
             break;
         }
     }
     //2.在现有组中没查找到
     if (!isFindInCurrentGroups) {
         List<T> newGroupList = new ArrayList<>();
         newGroupList.add(srcList.get(i));
         resultList.add(newGroupList);
     }
    

    }

    return resultList;
    }

  public static void main(String[] args) {

   List<JSONObject> jsonObjectList = new ArrayList<>();
   JSONObject jsonObject = new JSONObject();
   jsonObject.put("mark_id", 1);
   jsonObject.put("name", "1_张三");
   jsonObjectList.add(jsonObject);
  
   jsonObject = new JSONObject();
   jsonObject.put("mark_id", 1);
   jsonObject.put("name", "1_李四");
   jsonObjectList.add(jsonObject);
  
   jsonObject = new JSONObject();
   jsonObject.put("mark_id", 2);
   jsonObject.put("name", "2_kikop");
   jsonObjectList.add(jsonObject);
  
   List<List<JSONObject>> resultList=ListUtil.groupDataByCondition(jsonObjectList, new Comparator<JSONObject>() {
       @Override
       public int compare(JSONObject o1, JSONObject o2) {
           return o1.get("mark_id").equals(o2.get("mark_id")) ? 0 : -1;
       }
   });
  
   System.out.println(resultList);
  

  }

}