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JDK8 list＜object＞转map＜string,map＜string,list＜object＞＞＞并排序 示例
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先上测试代码： package com.lalala.test; import lombok.Data; import java.util.*; import java.util.stream.Collectors; /** * 类描述： * * @ClassName test * @Description TODO * @Author lalala * @Date 2023/8/18 11:12 * @Version 1.0 */ public class test { @Data static class Obj{ public Obj(String name, String sortNo, String dirName, String levelSort, String levelName) { this.name = name; this.sortNo = sortNo; this.dirName = dirName; this.levelSort = levelSort; this.levelName = levelName; } //序号 String sortNo; //目录名称 String dirName; //级次序号 String levelSort; //级次名称 String levelName; //名称 String name; } public static void main(String[] args) { List list = new ArrayList(); list.add(new Obj("name","1","d1","1","级次")); list.add(new Obj("name","5","d2","3","级次")); list.add(new Obj("name","2","d2","3","级次")); list.add(new Obj("name","5","d1","2","级次")); list.add(new Obj("name","2","d1","1","级次")); list.add(new Obj("name","3","d1","3","级次")); list.add(new Obj("name","1","d2","2","级次")); list.add(new Obj("name","4","d1","2","级次")); list.add(new Obj("name","4","d2","1","级次")); list.add(new Obj("name","3","d2","4","级次")); LinkedHashMap collect = list.stream() //1.1按照目录名称降序排序 默认升序 reversed()降序 .sorted(Comparator.comparing(Obj::getDirName).reversed()) .collect( //1.2按照目录名称分组 Collectors.groupingBy( dirOfObj -> dirOfObj.getDirName(), //方式一 分组+排序 LinkedHashMap::new, Collectors.collectingAndThen( //2.1按照级次序号+级次名称分组 Collectors.groupingBy( levelOfObj -> levelOfObj.getLevelSort() + "_" + levelOfObj.getLevelName(), LinkedHashMap::new, Collectors.collectingAndThen( Collectors.toList(), //3.按照序号排序 tolist -> { tolist.sort(Comparator.comparing(Obj::getSortNo)); return tolist; } ) ), //2.2按照级次序号排序 map -> { map = map.entrySet().stream().sorted( (o1, o2) -> o1.getKey().split("_")[0].compareTo(o2.getKey().split("_")[0]) ).collect(Collectors.toMap( Map.Entry::getKey, Map.Entry::getValue, (oldVal, newVal) -> oldVal, LinkedHashMap::new )); return map; } ) //方式二 分组不带排序 // Collectors.groupingBy( // levelOfObj -> levelOfObj.getLevelSort() + "_" + levelOfObj.getLevelName(), // LinkedHashMap::new, // Collectors.collectingAndThen( // Collectors.toList(), // tolist -> { // tolist.sort(Comparator.comparing(Obj::getSortNo)); // return tolist; // } // ) // ) ) ); System.out.println(list); System.out.println(collect); } }输出截图 1.初始list
2.转为map Map key1：目录名分组 --按照目录名称降序排序 key2：级次序号+级次名称分组 --按照级次序号升序排序 list分组后集合数据 --按照序号升序排序
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