如何从Hadoop中的Map程序输出具有列表等数据结构的自定义类

I am new to Hadoop and Map Reduce Programming. I have a dataset which contains Ratings about movies from 943 users. Each user has rated up to 20 movies. Now I want the output of my Mapper to be the User Id and a custom class which will have two lists for Movie (movie ids that the user rated) and the Ratings (Ratings for each Movie). But I am unsure how to output these values from the Map method in such a scenario. Code snippets Below:-I am new to Hadoop and Map Reduce Programming.