stream流 list转map

package com.mayikt.stream;  import com.mayikt.entity.UserEntity;  import java.util.ArrayList; import java.util.Map; import java.util.function.BiConsumer; import java.util.function.Function; import java.util.stream.Collectors; import java.util.stream.Stream;  /**  * @ClassName Test02  * @Author 蚂蚁课堂余胜军 QQ644064779 www.mayikt.com  * @Version V1.0  **/ public class Test02 {     public static void main(String[] args) {         ArrayList<UserEntity> userEntities = new ArrayList<>();         userEntities.add(new UserEntity("mayikt", 20));         userEntities.add(new UserEntity("meite", 28));         userEntities.add(new UserEntity("zhangsan", 35));          // list集合只有元素值 key list转换成map集合的情况下 指定key--user对象 username属性  value user对象         /**          * map<String(userName),UserEntity>          */         Stream<UserEntity> stream = userEntities.stream();         /**          * new Function<UserEntity(list集合中的类型), String(key map)>          */         Map<String, UserEntity> collect = stream.collect(Collectors.toMap(userEntity -> userEntity.getUserName(), userEntity -> userEntity));         collect.forEach((BiConsumer) (o, o2) -> System.out.println(o + "," + o2));     } }