1)sample data tk-no-MacBook-Pro:~ tk$ cat test.csv 01,8888888,9999999999 09,7777777,6666666666 02,2777333,9999992222 03,8888888,6567637476 2)select col2,col3 from ... where col1 = 09 tk-no-MacBook-Pro:~ tk$ awk -F, '{if ($1 == 09) print $2…

1) list of maps : sample list of maps 2) grouping and maxBy main codes 3) before and results appendix) to copy List<Optional<Map<String, Object>>> aggrList = mockList.stream().collect(Collectors.groupingBy(p -> (String)p.get("niveau_1")+ (String)p.get("niveau_2")+(Str</optional<map<string,>…