java - Sorting List in pairs without using Map or Sets -

i have strange problem in have data in 3 columns of students follows,

student    initdate      findate     abc   2/2/2016     5/5/2017     abc   3/2/2016     3/30/2017     ced   1/1/2015     3/12/2017     lef   1/12/2016    11/17/2017     ced   1/12/1999    12/23/207     lef   2/13/2000    11/19/2017 

my goal find lowest initdate of every student , highest findate of same student. data stored string have parse dates have done using dateformat parse date first.

initially, tried storing data in pair student,initdate , other pair student,findate, , tried storing data in hashmap date key problem store unique data , if 2 students have same initial dates 1 of them stored in hashmap.

i realized cannot use set , maps store data store unique values have decided use list.

i have created 3 lists, 1 of type string , other 2 of type date, can store duplicate data. have stored student names in 1 list , dates in other 2 lists.

what want sort list of students in such way initdate , findate sorted according student.

is there anyway sort 1 list based on other list in case of hashmaps ?

have considered writing own student class properties need , storing them list of student objects? can iterate through list of student objects find lowest value of init date , iterate through once more find highest fin date student id equal student id of first student object you've found.