中国建设工程招标网官方网站,wordpress 制作微信小程序,网站建设的程序,企业为什么要交税本文来说下Stream实现List和Map互转总结 文章目录 实体类Map转List代码List转Map代码 实体类 本篇介绍Stream流List和Map互转#xff0c;同时在转换过程中遇到的问题分析。 package cn.wideth.collect;import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.N… 本文来说下Stream实现List和Map互转总结 文章目录 实体类Map转List代码List转Map代码 实体类 本篇介绍Stream流List和Map互转同时在转换过程中遇到的问题分析。 package cn.wideth.collect;import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;Data
NoArgsConstructor
AllArgsConstructor
public class User {private Integer id;private String name;}Map转List代码 Map转List代码 package cn.wideth.collect;import lombok.extern.slf4j.Slf4j;import java.util.*;
import java.util.stream.Collectors;Slf4j
public class StreamMapToList {/*** 数据初始化*/private static final MapInteger, String mapToList;static{mapToList new HashMapInteger, String();mapToList.put(10088, ccc);mapToList.put(10086, aaa);mapToList.put(10087, bbb);}public static void main(String[] args) {ListUser userList defaultOrder();System.out.println(userList);ListUser userList2and orderByKeyMethodOne();System.out.println(userList2and);ListUser userList3and orderByKeyMethodTwo();System.out.println(userList3and);ListUser userList4and reverseOrderByKey();System.out.println(userList4and);ListUser userList5and orderByValue();System.out.println(userList5and);ListUser userList6and reverseOrderByValue();System.out.println(userList6and);}/***根据value倒序排序*/public static ListUser reverseOrderByValue(){ListUser userList mapToList.entrySet().stream().sorted(Collections.reverseOrder(Map.Entry.comparingByValue())).map(a - new User(a.getKey(),a.getValue())).collect(Collectors.toList());return userList;}/*** 根据value排序*/public static ListUser orderByValue(){ListUser userList mapToList.entrySet().stream().sorted(Comparator.comparing(Map.Entry::getValue)).map(a - new User(a.getKey(), a.getValue())).collect(Collectors.toList());return userList;}/***根据key倒序排序*/public static ListUser reverseOrderByKey(){ListUser userList mapToList.entrySet().stream().sorted(Map.Entry.comparingByKey(Comparator.reverseOrder())).map(a - new User(a.getKey(),a.getValue())).collect(Collectors.toList());return userList;}/***根据key排序方法2*/public static ListUser orderByKeyMethodTwo(){ListUser userList mapToList.entrySet().stream().sorted(Map.Entry.comparingByKey()).map(a - new User(a.getKey(),a.getValue())).collect(Collectors.toList());return userList;}/***根据key排序方法1*/private static ListUser orderByKeyMethodOne() {ListUser userList mapToList.entrySet().stream().sorted(Comparator.comparing(a - a.getKey())).map(a - new User(a.getKey(),a.getValue())).collect(Collectors.toList());return userList;}/*** 按照默认顺序*/private static ListUser defaultOrder() {ListUser userList mapToList.entrySet().stream().map(a - new User(a.getKey(), a.getValue())).collect(Collectors.toList());return userList;}
} 测试结果 List转Map代码 List转Map package cn.wideth.collect;import lombok.extern.slf4j.Slf4j;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;Slf4j
public class StreamListToMap {private static final ListUser userList;static{userList Arrays.asList(new User(1003,keko),new User(1001,jeek),new User(1002,mack));}public static void main(String[] args) {MapInteger, String listToMap1 method01();System.out.println(listToMap1);MapInteger, User listToMap2 method02();System.out.println(listToMap2);MapInteger, User listToMap3 method03();System.out.println(listToMap3);MapInteger, User listToMap4 method04();System.out.println(listToMap4);}/*** 指定key-valuevalue是对象中的某个属性值*/public static MapInteger,String method01(){MapInteger, String userMap userList.stream().collect(Collectors.toMap(User::getId, User::getName));return userMap;}/***指定key-valuevalue是对象本身User-User 是一个返回本身的lambda表达式*/public static MapInteger,User method02(){MapInteger, User userMap userList.stream().collect(Collectors.toMap(User::getId, User-User));return userMap;}/*** 指定key-valuevalue是对象本身Function.identity()是简洁写法也是返回对象本身*/public static MapInteger,User method03(){MapInteger, User userMap userList.stream().collect(Collectors.toMap(User::getId, Function.identity()));return userMap;}/*** 指定key-value,key 冲突的解决办法* (key1,key2)-key2:第二个key覆盖第一个key* (key1,key2)-key1:保留第一个key*/public static MapInteger,User method04(){MapInteger, User userMap userList.stream().collect(Collectors.toMap(User::getId, Function.identity(),(key1,key2)-key2));return userMap;}} 测试结果
