Hey, you are on the right track , when you create an ArrayList of TiingoCandle, it basically maps your JSON to your java object.
You basically have an arrayList of all the values from startDate to endDate.
Now your task is to take the last value in this list. ->(For closing Price, it requires the value from the lastDate of your API call).
You can now make use of a DataStructure like HashMap or a HashSet to use it to sort the Symbols on the basis of its closing values
OR you can refer to this reference given under the taskboard.
This uses a compareTo() function in the TotalReturnsDTO POJO , you can sort on the basis of the values provided in this POJO.
You can refer to this FAQ, if you are getting any further errors.
You can tag me, if you have any doubts.
Hope I have solved your problem now